Treatment liquid for semiconductor with ruthenium and method of producing the same

ABSTRACT

Provided is a treatment liquid for a semiconductor with ruthenium, containing a hypobromite ion. Also provided is a treatment liquid for a semiconductor with ruthenium, containing at least a bromine-containing compound, an oxidizing agent, a basic compound, and water which are added and mixed, wherein the liquid has the bromine-containing compound added in an amount of 0.01 mass % or more and less than 2 mass % as a bromine element content with respect to the total mass of the liquid, has the oxidizing agent added in an amount of 0.1 mass % or more and 10 mass % or less with respect to the total mass, and has a pH of 8 or more and 14 or less. Further provided is a method of producing a treatment liquid for a semiconductor with ruthenium, including a step of mixing a bromine-containing compound with a solution containing a hypochlorous acid compound and a basic compound.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a treatment liquid used to carry outetching or the like on ruthenium in a semiconductor wafer containing theruthenium in production processes of semiconductor elements.

Background Art

In recent years, microfabrication design has been promoted for thedesign rule for semiconductor elements, and thus the wiring resistancetends to increase. As a result of the increase in wiring resistance, thehigh-speed operation of a semiconductor element is markedly impaired,thus making it necessary to take countermeasures. In view of this, adesired wiring material is a wiring material having lowerelectromigration resistance and a lower resistance value thanconventional wiring materials.

Ruthenium has higher electromigration resistance than aluminum andcopper which are conventional wiring materials, and ruthenium candecrease the resistance value of the wiring, thus attracting attentionparticularly as a wiring material for which the design rule forsemiconductor elements is 10 nm or less. Not only in cases whereruthenium is used as a wiring material but also in cases where copper isused as a wiring material, ruthenium can prevent electromigration, andthus, using ruthenium as a barrier metal for copper wiring is understudy.

In cases where ruthenium is selected as a wiring material in a wiringformation step of a semiconductor element, the wiring is formed by dryor wet etching in the same manner as in cases where a conventionalwiring material is used. However, ruthenium is difficult to remove bydry etching with etching gas or etching by CMP polishing, and thus, moreprecise etching is desired; specifically, wet etching is attractingattention.

In cases where ruthenium is subjected to wet etching, the dissolutionrate, in other words, etching rate of ruthenium is important. If theetching rate is high, ruthenium can be dissolved in a short time, thusmaking it possible to increase the number of wafers to be treated perunit time.

In cases where ruthenium is subjected to wet etching under alkalineconditions, ruthenium is dissolved, for example, in the form of RuO₄ ⁻or RuO₄ ²⁻ in a treatment liquid. RuO₄ ⁻ or RuO₄ ²⁻ is changed to RuO₄in a treatment liquid, and part of the RuO₄ is gasified and releasedinto a gas phase. RuO₄ is strongly oxidative, and thus, not only isharmful to the human body but also is easily reduced to generate RuO₂particles. In general, particles cause a decrease in the yield rate, andthus, are very problematic in semiconductor formation steps. Againstsuch a background, it is very important to inhibit the generation ofRuO₄ gas.

Patent Document 1 discloses that such a treatment liquid to be used toremove ruthenium from a semiconductor wafer by etching is that treatmentliquid for a wafer having ruthenium which contains a hypochlorite ionand a solvent and has a pH of more than 7 and less than 12.0 at 25° C.The liquid contains a hypochlorite ion, and is shown to be capable ofremoving ruthenium and tungsten sticking to the end face portion andback face portion of a semiconductor wafer.

Patent Document 2 describes a ruthenium metallic etching compositioncharacterized by being formed by adding and mixing a bromine-containingcompound, an oxidizing agent, a basic compound, and water, and has thebromine-containing compound added in an amount of 2 to 25 mass % as abromine element content with respect to the total mass of thecomposition, the oxidizing agent added in an amount of 0.1 to 12 mass %,and a pH of 10 or more and less than 12.

CITATION LIST Patent Documents

Patent Document 1: WO 2019/142788

Patent Document 2: WO 2011/074601

SUMMARY OF THE INVENTION

In order to remove ruthenium from a semiconductor wafer having rutheniumby etching, it is important to satisfy both the etching rate ofruthenium and the inhibition of RuO₄ gas. However, the presentinventors' studies have revealed that the conventional treatment liquidsdescribed in the prior art documents have room for improvement in thebelow-mentioned respects.

For example, Patent Document 1 describes a treatment liquid having a pHof more than 7 and less than 12.0 as a treatment liquid for a waferhaving ruthenium. The treatment liquid described in Patent Document 1has a sufficient etching rate of ruthenium, but nothing is mentionedabout RuO₄ gas, and actually, the method described in Patent Document 1was not capable of inhibiting the generation of RuO₄ gas. In otherwords, for the treatment liquid of wafer having ruthenium described inPatent Document 1, it is difficult to satisfy both the etching rate ofruthenium and the control of RuO₄ gas.

A ruthenium metallic etching composition described in Patent Document 2is characterized by having a pH of 10 or more and less than 12, but inthis pH range, etching of ruthenium is accompanied by the generation ofRuO₄ gas, and thus, the composition has room for improvement. Inaddition, Patent Document 2 mentions nothing about the inhibition ofRuO₄ gas, and actually, the method described in Patent Document 2 wasnot capable of inhibiting the generation of RuO₄ gas. In addition, theetching composition has a problem in that the composition has poorchemical liquid stability and greatly varies the etching rate ofruthenium with time. Furthermore, in the method described as a method ofpreparing the treatment liquid, the bromine-containing compound isoxidized by the oxidizing agent under acidic conditions to obtain anoxide, which is then mixed with a basic compound to have a pH suitablyadjusted to basicity, but the method has room for improvement in thehandling of the treatment liquid, for example, because the oxide and thebasic compound are mixed and allowed to stand for several hours untilbromine gas is generated, and because a high concentration of the basiccompound needs to be added in a large amount to adjust the pH fromacidity to basicity. Accordingly, the present invention has been made inview of the above-mentioned background technology, and an object of thepresent invention is to provide a treatment liquid and a method ofproducing the same, wherein the treatment liquid makes it possible toetch, at a sufficient rate, ruthenium sticking to the front face, endface portion, and back face portion of a semiconductor wafer, to allowthe rate to have excellent stability, and to inhibit the generation ofRuO₄ gas.

Solution to Problem

To solve the above-mentioned problems, the present inventors have madestudies vigorously. Then, the present inventors have discovered thattreating ruthenium with a treatment liquid containing a hypobromite ionmakes it possible to etch ruthenium at a high rate. Furthermore, thepresent inventors have discovered that a bromine-containing compoundadded to an alkaline treatment liquid is oxidized by an oxidizing agentin the treatment liquid to become a bromine oxide, thus making itpossible to etch ruthenium at a high rate. The present inventors havefurther discovered that suitably selecting the pH range, theconcentration range of the bromine-containing compound, and theconcentration range of the oxidizing agent makes it possible to keep thesufficient etching rate stable and inhibit the generation of RuO₄ gas;and have come to complete the present invention.

In other words, the present invention is constituted by thebelow-mentioned aspects.

Aspect 1: a treatment liquid for a semiconductor with ruthenium,containing a hypobromite ion.

Aspect 2: the treatment liquid for a semiconductor according to Aspect1, wherein the hypobromite ion content is 0.001 mol/L or more and 0.20mol/L or less.

Aspect 3: the treatment liquid for a semiconductor according to Aspect 1or 2, wherein the hypobromite ion content is 0.01 mol/L or more and 0.10mol/L or less.

Aspect 4: the treatment liquid for a semiconductor according to any oneof Aspects 1 to 3, wherein the treatment liquid for a semiconductorfurther contains an oxidizing agent, and the oxidation-reductionpotential of the oxidizing agent exceeds the oxidation-reductionpotential of the hypobromite ion/Br⁻ system.

Aspect 5: the treatment liquid for a semiconductor according to Aspect4, wherein the oxidizing agent contained in the treatment liquid for asemiconductor is a hypochlorite ion or ozone.

Aspect 6: the treatment liquid for a semiconductor according to any oneof Aspects 1 to 5, further containing a tetraalkylammonium ion.

Aspect 7: the treatment liquid for a semiconductor according to Aspect6, wherein the tetraalkylammonium ion is a tetramethylammonium ion.

Aspect 8: the treatment liquid for a semiconductor according to any oneof Aspects 1 to 7, wherein the proportion of the hypobromite ion in 1mol of bromine element contained in the treatment liquid for asemiconductor is more than 0.5 mol.

Aspect 9: the treatment liquid for a semiconductor according to any oneof Aspects 1 to 8, wherein the treatment liquid has a pH of 8 or moreand 14 or less.

Aspect 10: the treatment liquid for a semiconductor according to any oneof Aspects 1 to 9, wherein the treatment liquid has a pH of 12 or moreand less than 13.

Aspect 11: a treatment liquid for a semiconductor with ruthenium,containing at least a bromine-containing compound, an oxidizing agent, abasic compound, and water, wherein the treatment liquid has thebromine-containing compound added in an amount of 0.008 mass % or moreand less than 10 mass % as a bromine element content with respect to thetotal mass of the treatment liquid, has the oxidizing agent added in anamount of 0.1 mass ppm or more and 10 mass % or less with respect to thetotal mass, and has a pH of 8 or more and 14 or less.

Aspect 12: the treatment liquid for a semiconductor with rutheniumaccording to Aspect 11, having the bromine-containing compound added inan amount of 0.08 mass % or more and less than 2.0 mass % as a bromineelement content.

Aspect 13: the treatment liquid for a semiconductor with rutheniumaccording to Aspect 11 or 12, having the bromine-containing compoundadded in an amount of 0.01 mass % or more and less than 2 mass % as abromine element content, and having the oxidizing agent added in anamount of 0.1 mass % or more and 10 mass % or less.

Aspect 14: the treatment liquid for a semiconductor according to any oneof Aspects 11 to 13, wherein the ruthenium is a ruthenium metal or aruthenium alloy.

Aspect 15: the treatment liquid for a semiconductor according to any oneof Aspects 11 to 14, wherein the oxidizing agent is a hypochlorous acidcompound or ozone.

Aspect 16: the treatment liquid for a semiconductor according to any oneof Aspects 11 to 15, wherein the bromine-containing compound is abromine salt or hydrogen bromide.

Aspect 17: the treatment liquid for a semiconductor according to Aspect16, wherein the bromine salt is a tetraalkylammonium bromide.

Aspect 18: the treatment liquid for a semiconductor according to Aspect17, wherein the tetraalkylammonium bromide is a tetramethylammoniumbromide.

Aspect 19: the treatment liquid for a semiconductor according to any oneof Aspects 11 to 18, wherein the basic compound is a tetramethylammoniumhydroxide.

Aspect 20: the treatment liquid for a semiconductor according to any oneof Aspects 11 to 19, wherein the pH is 12 or more and 14 or less.

Aspect 21: the treatment liquid for a semiconductor according to any oneof Aspects 11 to 20, wherein the pH is 12 or more and less than 13.

Aspect 22: the treatment liquid for a semiconductor according to Aspect14, wherein the ruthenium metal contains 70 at. % or more of ruthenium.

Aspect 23: the treatment liquid for a semiconductor according to Aspect14, wherein the ruthenium metal is a metallic ruthenium.

Aspect 24: the treatment liquid for a semiconductor according to Aspect14, wherein the ruthenium alloy contains 70 at. % or more and 99.99 at.% or less of ruthenium.

Aspect 25: the treatment liquid for a semiconductor according to any oneof Aspects 11 to 24, wherein the proportion of the hypobromite ion in 1mol of bromine element contained in the treatment liquid for asemiconductor is more than 0.5 mol.

Aspect 26: a method of producing the treatment liquid for asemiconductor according to any one of Aspects 11 to 25, including a stepof mixing the bromine-containing compound and a solution containing boththe oxidizing agent and the basic compound.

Aspect 27: a method of producing the treatment liquid for asemiconductor according to any one of Aspects 11 to 25, including a stepof mixing the bromine-containing compound into an aqueous solution ofboth the oxidizing agent and the basic compound.

Aspect 28: a method of treating a substrate, including the steps of:producing a treatment liquid for a semiconductor by the productionmethod according to Aspect 26 or 27; and then using the treatment liquidfor a semiconductor to etch a ruthenium metal film and/or a rutheniumalloy film deposited on the substrate.

Aspect 29: a method of producing a treatment liquid for a semiconductorwith ruthenium, including a step of mixing a hypobromous acid, ahypobromite, a bromine water, or a bromine gas with a solutioncontaining a basic compound.

Aspect 30: a method of producing a treatment liquid for a semiconductorwith ruthenium, including a step of mixing a bromine-containing compoundwith a solution containing a hypochlorous acid compound and a basiccompound.

Aspect 31: the method of producing a treatment liquid for asemiconductor according to Aspect 30, wherein a step of mixing abromine-containing compound with a solution containing a hypochlorousacid compound and a basic compound is a step in which thebromine-containing compound is added to and mixed into the solutioncontaining the hypochlorous acid compound and the basic compound.

Aspect 32: the method of producing a treatment liquid for asemiconductor according to any one of Aspects 29 to 31, wherein thesolution is an aqueous solution.

Aspect 33: the production method according to any one of Aspects 29 to32, wherein the ruthenium is a ruthenium metal or a ruthenium alloy.

Aspect 34: the method of producing a treatment liquid for asemiconductor according to any one of Aspects 29 to 33, wherein thebasic compound is a tetramethylammonium hydroxide.

Aspect 35: the method of producing a treatment liquid for asemiconductor according to any one of Aspects 30 to 34, wherein thebromine-containing compound is a bromine salt or hydrogen bromide.

Aspect 36: the method of producing a treatment liquid for asemiconductor according to Aspect 35, wherein the bromine salt is anonium bromide.

Aspect 37: the method of producing a treatment liquid for asemiconductor according to Aspect 36, wherein the onium bromide is aquaternary onium bromide or a tertiary onium bromide.

Aspect 38: the method of producing a treatment liquid for asemiconductor according to Aspect 37, wherein the quaternary oniumbromide is a tetraalkylammonium bromide.

Aspect 39: the method of producing a treatment liquid for asemiconductor according to Aspect 38, wherein the tetraalkylammoniumbromide is produced from a tetraalkylammonium hydroxide and a bromideion.

Aspect 40: the method of producing a treatment liquid for asemiconductor according to Aspect 38 or 39, wherein thetetraalkylammonium bromide is produced from a tetraalkylammoniumhydroxide and hydrogen bromide.

Aspect 41: the method of producing a treatment liquid for asemiconductor according to Aspect 35, wherein the bromine salt isammonium bromide, sodium bromide, or potassium bromide.

Aspect 42: the method of producing a treatment liquid for asemiconductor according to any one of Aspects 30 to 41, wherein thesolution containing the hypochlorous acid compound is atetraalkylammonium hypochlorite solution.

Aspect 43: the method of producing a treatment liquid for asemiconductor according to Aspect 42, including a step of producing thetetraalkylammonium hypochlorite solution, wherein the step includes apreparation step of providing a tetraalkylammonium hydroxide solutionand a reaction step of contacting the tetraalkylammonium hydroxidesolution with chlorine, and wherein the concentration of carbon dioxidein the gas phase portion in the reaction step is 100 vol ppm or less,and the pH of the liquid phase portion in the reaction step is 10.5 ormore.

Aspect 44: the method of producing a treatment liquid for asemiconductor according to Aspect 43, wherein the carbon number of eachalkyl group of the tetraalkylammonium hydroxide provided in thepreparation step is 1 to 10.

Aspect 45: the method of producing a treatment liquid for asemiconductor according to Aspect 43 or 44, wherein the reactiontemperature in the reaction step is −35° C. or more and 25° C. or less.

Aspect 46: the method of producing a treatment liquid for asemiconductor according to any one of Aspects 43 to 45, wherein theconcentration of carbon dioxide in the tetraalkylammonium hydroxidesolution in the reaction step is 0.001 ppm or more and 500 ppm or less.

Effects of the Invention

The present invention makes it possible to subject ruthenium to wetetching stably at a sufficiently high rate and inhibit the generation ofRuO₄ gas in semiconductor formation steps. This makes it possible notonly to enhance the wafer treatment efficiency per unit time, but alsoto inhibit the yield rate from being decreased by RuO₂ particles, and tocarry out treatment safe for the human body, thus satisfying both theproduction cost and safety.

Furthermore, the method according to the present invention makes itpossible to directly oxidize a bromine-containing compound with anoxidizing agent in an alkaline treatment liquid and thus promptlyproduce bromine, hypobromous acid, hypobromite ion, bromous acid,bromite ion, bromic acid, bromate ion, perbromic acid, and perbromateion. A treatment liquid produced in this manner contains a hypobromiteion, thus making it possible to etch ruthenium immediately withoutwaiting the generation of bromine gas for a long time and to shorten thetime required for semiconductor production.

Furthermore, the pH of the treatment liquid does not need to be adjustedfrom acidity to alkalinity, thus making it possible to significantlydecrease the amount of the basic compound to be added to the treatmentliquid, and making the handling of the treatment liquid easier.

DESCRIPTION OF THE EMBODIMENTS

(Treatment Liquid for a Semiconductor)

The treatment liquid according to the present invention is characterizedby containing a hypobromite ion (BrO⁻). The hypobromite ion is astrongly oxidative oxidizing agent, and the treatment liquid containinga hypobromite ion according to the present invention makes it possibleto etch ruthenium at a high rate under alkaline conditions. Furthermore,suitably selecting the pH of the treatment liquid and the kind andconcentration of the oxidizing agent makes it possible to etch rutheniumat a stable etching rate while the generation of RuO₄ gas is inhibited.Because of this, the treatment liquid according to the present inventioncan be suitably used in an etching step, a residue removal step, awashing step, a CMP step, and the like in semiconductor productionprocesses. As used herein, a semiconductor with ruthenium refers to asemiconductor containing ruthenium.

Use of the treatment liquid according to the present invention makes itpossible to inhibit the generation of RuO₄ gas and remove, at asufficient etching rate, ruthenium sticking to the front face, end faceportion, and back face portion of a semiconductor wafer. In the presentinvention, a sufficient etching rate refers to an etching rate of 10Å/min or more. The etching rate of 10 Å/min or more for ruthenium makesit possible that the treatment liquid is suitably used in an etchingstep, a residue removal step, a washing step, a CMP step, and the like.In addition, the amount of RuO₄ gas generated when ruthenium is etcheddepends on the treatment conditions (for example, the amount ofdissolved ruthenium, the volume of the treatment liquid used, thetreatment temperature, the volume and material of a container or achamber, and the like). Accordingly, in comparison of the generationamounts of RuO₄ gas, it is important to consider these conditions, andin a simplified manner, the amounts can be evaluated as the generationamounts per unit area of a wafer containing ruthenium. The generationamount of RuO₄ per unit area of a wafer containing ruthenium can bedetermined by: trapping the RuO₄ gas generated during etching in asuitable absorbing liquid (for example, an alkaline solution such as anaqueous NaOH solution), quantitating the amount of the ruthenium in thetrapping liquid, and then dividing the amount by the area of the waferused. Accordingly, the generation amounts of RuO₄ gas per unit area canbe compared to verify the RuO₄ gas inhibition effect. A treatment liquidwhich generates a smaller amount of RuO₄ per unit area makes it possibleto inhibit the generation of the RuO₄ gas and inhibit the generation ofRuO₂ particles, and thus, can be suitably used for etching of ruthenium.

The treatment liquid in the present invention can etch ruthenium, butdoes not etch a metal such as copper, cobalt, titanium, platinum,titanium nitride, or tantalum nitride, or etches such a metal at a verylow etching rate, compared with a ruthenium metal. Because of this, itis also possible to selectively etch a ruthenium metal without damaginga substrate material containing a metal of them in semiconductorproduction processes and the like.

In the present invention, that the etching rate of ruthenium is stablemeans that the rate at which ruthenium is etched with a treatment liquidcontaining a hypobromite ion does not change over time. Specifically,the meaning is that, in cases where a plurality of wafers havingruthenium are etched using the same treatment liquid (assuming that thenumber of wafers is n), the etching rate of ruthenium in the first waferis substantially the same as the etching rate of ruthenium in the nthwafer. Here, being substantially the same means that the range ofvariation of the etching rate of ruthenium in the nth wafer with respectto the etching rate of ruthenium in the first wafer, in other words, anincrease/decrease in the etching rate is within ±20%. In addition, aperiod of time during which an increase/decrease between the etchingrate of ruthenium in the nth wafer and the etching rate of ruthenium inthe first wafer is within ±20% is defined as the stability time of theetching rate. A suitable value as the stability time of the etching ratevaries depending on the condition and production process under which atreatment liquid according to the present invention is used, and forexample, a treatment liquid which allows the stability time of theetching rate to be one hour or more can be suitably used forsemiconductor production processes. Considering the possibility ofhaving enough time for handling of the treatment liquid and thepossibility of setting the process time in a flexible manner, atreatment liquid allowing the stability time of the etching rate to be10 hours or more is more preferable.

A treatment liquid which does not allow the etching rate of ruthenium tochange over time or a treatment liquid which allows the stability timeof the etching rate to be long makes it possible not only to subjectruthenium to etching stably using the treatment liquid in semiconductorproduction processes but also to reutilize (reuse) the treatment liquid,and thus, such a treatment liquid is excellent in terms of productivityand cost.

A hypobromite ion contained in a treatment liquid according to thepresent invention may be generated in the treatment liquid, or ahypobromite may be added to the treatment liquid. As used herein, ahypobromite refers to a salt containing a hypobromite ion or a solutioncontaining the salt. To generate a hypobromite ion in the treatmentliquid, for example, bromine gas can be sparged into the treatmentliquid. In this case, the treatment liquid is preferably at 50° C. orless in terms of generating a hypobromite ion efficiently. Causing thetreatment liquid to be at 50° C. or less makes it possible not only togenerate a hypobromite ion efficiently but also to use the generatedhypobromite ion to etch ruthenium stably. Furthermore, to dissolve alarger amount of bromine in the treatment liquid, the temperature of thetreatment liquid is more preferably 30° C. or less, most preferably 25°C. or less. The lower limit of the temperature of the treatment liquidis not limited to any particular value, but the treatment liquid ispreferably not frozen. Accordingly, the treatment liquid is preferablyat −35° C. or more, more preferably −15° C. or more, most preferably 0°C. or more. The treatment liquid into which the bromine gas is spargedis not limited to any particular pH, but a treatment liquid having analkaline pH value can be used to etch ruthenium immediately after ahypobromite ion is generated.

Furthermore, in cases where a hypobromite ion is generated by spargingbromine gas into a treatment liquid containing a bromide ion (Br⁻), thetreatment liquid enhances the solubility of the bromine gas (Br₂). Thisis because Br₂ dissolved in the treatment liquid reacts with Br⁻ and Br₃⁻ to form a complex ion such as Br₃ ⁻ and Br₅ ⁻, and is stabilized inthe treatment liquid. The treatment liquid containing Br₂, Br⁻, Br₃ ⁻,Br₅ ⁻, and the like in larger amounts can generate a hypobromite ion ina larger amount, and thus, can be suitably used as a treatment liquidaccording to the present invention.

Oxidizing a bromine-containing compound with an oxidizing agent alsomakes it possible to produce a hypobromite ion in the treatment liquid.

To add a hypobromite ion in the form of a compound to the treatmentliquid, it is only necessary to add a hypobromous acid, bromine water,and/or hypobromite. A suitable hypobromite is sodium hypobromite,potassium hypobromite, or tetraalkylammonium hypobromite; a hypobromousacid or tetraalkylammonium hypobromite is more suitable in terms ofcontaining no metal ion which is problematic in semiconductorproduction.

The tetraalkylammonium hypobromite is easily obtained by passing brominegas through a tetraalkylammonium hydroxide solution. Alternatively, thetetraalkylammonium hypobromite is obtained by mixing a hypobromous acidand a tetraalkylammonium hydroxide solution. Furthermore, thetetraalkylammonium hypobromite can be obtained also by using an ionexchange resin to cause a cation contained in a hypobromite such assodium hypobromite to be replaced with a tetraalkylammonium ion.

The concentration of the hypobromite ion in a treatment liquid accordingto the present invention is not limited to any particular value as longas the value does not depart from the object of the present invention,and the concentration is preferably 0.001 mol/L or more and 0.20 mol/Lor less as the amount of the bromine element contained in thehypobromite ion. The amount of less than 0.001 mol/L results in causingruthenium to be etched at a low rate, and is not very practicable. Inaddition, the amount of more than 0.20 mol/L causes a hypobromite ion tobe more likely to be decomposed, and thus, the etching rate of rutheniumresults in being less likely to be stable. To etch ruthenium stably at asufficient rate, the concentration of the hypobromite ion is preferably0.001 mol/L or more and 0.20 mol/L or less, more preferably 0.005 mol/Lor more and 0.20 mol/L or less, most preferably 0.01 mol/L or more and0.10 mol/L or less, as the amount of the bromine element contained in ahypobromite ion.

To moderate a decrease in the etching rate of ruthenium and stabilizethe etching rate, the proportion of hypobromite ions in 1 mol of bromineelement contained in the treatment liquid is preferably more than 0.5mol. As above-mentioned, a hypobromite ion is easily changed to Br⁻ bythe oxidization reaction or decomposition reaction of ruthenium. Br⁻does not etch ruthenium, and thus, for stable ruthenium etching, it isimportant to promptly oxidize Br⁻ in the treatment liquid into ahypobromite ion so as to keep a high concentration of chemical species(a hypobromite ion: BrO⁻) having high ruthenium etching capability. Incases where the proportion of a hypobromite ion in 1 mol of bromineelement contained in a treatment liquid according to the presentinvention is more than 0.5 mol, in other words, in cases where thebromine element more than half, in number, of all bromine element in thetreatment liquid is present in the form of BrO⁻, the concentration ofthe chemical species having ruthenium etching capability can be regardedas sufficiently high, and the etching rate of ruthenium is stabilized.

The concentration of a hypobromite ion in the treatment liquid can beverified using a widely known method. For example, ultraviolet andvisible absorptiometry is used to easily verify absorption due to ahypobromite ion, and the hypobromite ion concentration can be determinedfrom the intensity of an absorption peak (generally approximately 330 nmalthough depending on the pH, hypobromite ion concentration, or the likeof the treatment liquid). In addition, the hypobromite ion concentrationcan be determined also by iodine titration. Besides, the hypobromite ionconcentration can be determined from the oxidation-reduction potential(ORP) or pH of the treatment liquid. Measurement by ultraviolet andvisible absorptiometry is most preferable in terms of making contactlessand continuous measurement possible. In this regard, when thehypobromite ion concentration is measured by ultraviolet and visibleabsorptiometry and when absorption by (an)other chemical species isfound, carrying out data processing, such as spectral splitting andbaseline correction, and suitable selection of a reference enables thehypobromite ion concentration to be determined with sufficient accuracy.

The acid dissociation constant (pK_(a)) of a hypobromous acid (HBrO) anda hypobromite ion (BrO⁻) is 8.6, and thus, HBrO and BrO⁻ coexist in somecases depending on the pH of the treatment liquid, for example, in caseswhere the pH is low. In cases where the treatment liquid contains HBrOand BrO⁻, the total concentration of HBrO and BrO⁻ can be regarded asthe above-mentioned hypobromite ion concentration.

The detail of the mechanism by which a hypobromite ion dissolvesruthenium is not necessarily clear, but the inference is that ahypobromite ion or hypobromous acid generated from a hypobromite ionoxidizes ruthenium in the treatment liquid to form RuO₄, RuO₄ ⁻, or RuO₄²⁻, which are dissolved in the treatment liquid. Causing ruthenium to bedissolved in the form of RuO₄ ⁻ or RuO₄ ²⁻ makes it possible to decreasethe generation amount of RuO₄ gas and inhibit the generation of RuO₂particles. To dissolve ruthenium in the form of RuO₄ ⁻ or RuO₄ ²⁻, thepH of the treatment liquid is preferably alkaline, the pH of thetreatment liquid is more preferably 8 or more and 14 or less, the pH isstill more preferably 12 or more and 14 or less, and the pH is mostpreferably 12 or more and less than 13. The treatment liquid having a pHof 12 or more and less than 13 causes ruthenium to be dissolved in theform of RuO₄ ⁻ or RuO₄ ²⁻ in the treatment liquid, thus making itpossible to significantly decrease the generation amount of RuO₄ gas andinhibit the generation of RuO₂ particles. In addition, in cases wherethe pH of the treatment liquid is less than 8, ruthenium is more easilyoxidized to RuO₂ or RuO₄, thus increasing the amount of RuO₂ particlesand tending to increase the generation amount of RuO₄ gas. In addition,the pH of more than 14 causes ruthenium to be dissolved less easily,making it difficult to obtain a sufficient ruthenium etching rate, andthus, decreases the production efficiency in semiconductor production.

To adjust the pH of the treatment liquid, acid or alkali can be added tothe treatment liquid. The acid may be either an inorganic acid or anorganic acid, examples of which include hydrofluoric acid, hydrochloricacid, hydrobromic acid, nitric acid, sulfuric acid, peroxodisulfuricacid, carboxylic acids such as formic acid, and acetic acid; andbesides, other widely known acids can be used for a treatment liquid fora semiconductor without any limitation. The alkali to be preferably usedis an organic alkali, because such an alkali contains no metal ionproblematic in semiconductor production. Examples of organic alkalisinclude a tetraalkylammonium hydroxide composed of a tetraalkylammoniumion and a hydroxide ion. Examples of the tetraalkylammonium hydroxideinclude tetramethylammonium hydroxide, tetraethylammonium hydroxide,tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and thelike. Among these, the organic alkali is preferably tetraalkylammoniumhydroxide, more preferably tetramethylammonium hydroxide, in terms ofthe large number of hydroxide ions per unit weight and in terms of beingeasily available in the form of a high purity product.

The above-mentioned tetraalkylammonium ions to be contained in thetreatment liquid may be used singly or in combination of two or morekinds thereof.

A treatment liquid according to the present invention preferablycontains an oxidizing agent. An oxidizing agent contained in thetreatment liquid according to the present invention plays a role whichis to cause a bromide ion (Br⁻) generated by decomposition of ahypobromite ion to be oxidized back into a hypobromite ion.

When ruthenium is oxidized, the hypobromite ion is reduced to Br⁻. Inaddition, hypobromite ions are naturally decomposed easily in thetreatment liquid, and part thereof changes to Br⁻. Furthermore, thedecomposition of hypobromite ions is promoted by ultraviolet light andvisible light, and part of the ions change to Br⁻. Furthermore, thedecomposition of the hypobromite ions is promoted by heating, contactwith acid, or contact with metal, and thus, part of the ions changesBr⁻. Br⁻ generated by the reduction or decomposition of the hypobromiteions does not dissolve ruthenium, and thus, the promoted reduction ordecomposition of the hypobromite ions decreases the etching rate ofruthenium. The treatment liquid containing a suitable oxidizing agentenables Br⁻ generated by the reduction or decomposition to be oxidizedinto hypobromite ions, and makes it possible to moderate a decrease inthe etching rate of ruthenium. In other words, the treatment liquidcontaining a hypobromite ion and a suitable oxidizing agent lengthensthe stability time of the etching rate.

An oxidizing agent which may be contained in the treatment liquid ispreferably such that the oxidation-reduction potential between theoxidizing agent and the chemical species generated by the reduction ofthe oxidizing agent exceeds the oxidation-reduction potential of thehypobromite ion/Br⁻ system. Use of such an oxidizing agent enables Br⁻to be oxidized into a hypobromite ion. The oxidation-reduction potentialbetween the oxidizing agent which may be contained in the treatmentliquid and the chemical species generated by the reduction of theoxidizing agent changes depending on the concentration of each of theoxidizing agent and the chemical species generated by the reduction ofthe oxidizing agent, the temperature and pH of the solution, and thelike, but independent of these conditions, the oxidation-reductionpotential between the oxidizing agent and the chemical species generatedby the reduction of the oxidizing agent only needs to exceed theoxidation-reduction potential of the hypobromite ion/Br⁻ system.

In addition, for the oxidizing agent which may be contained in thetreatment liquid, the oxidation-reduction potential between theoxidizing agent and the chemical species generated by the reduction ofthe oxidizing agent is not limited to any particular upper limit as longas the upper limit does not depart from the object of the presentinvention. However, in cases where the oxidation-reduction potential ishigher than the oxidation-reduction potential of the RuO₄ ⁻/RuO₄ system(1.0 V vs. SHE), RuO₄ ⁻ dissolved in the treatment liquid is oxidizedinto RuO₄ by the oxidizing agent, causing the possibility that thegeneration of RuO₄ gas increases. In such a case, suitably adjusting theamount of an oxidizing agent to be added to the treatment liquid and thetiming of addition of the oxidizing agent makes it possible to inhibitthe oxidation of RuO₄ ⁻ into RuO₄ and control the generation amount ofRuO₄ gas.

The oxidizing agent which may be contained in the treatment liquidaccording to the present invention does not contain any metal elementwhich is problematic in semiconductor production, and thus, ahypochlorite ion or ozone is preferably utilized. Among these, ahypochlorite ion is more suitable in terms of the high solubility in thetreatment liquid, the stable presence in the solution, and the easinessof the concentration adjustment.

A hypochlorite ion and ozone have the capability to reoxidize Br⁻ into ahypobromite ion in an alkaline treatment liquid (having a pH of 8 ormore and 14 or less). This is also understood from the fact that theoxidation-reduction potential of the hypochlorite ion/Cl⁻ system is 0.89V, and that the oxidation-reduction potential of the ozone/oxygen systemis 1.24 V, but that the oxidation-reduction potential of the hypobromiteion/Br⁻ system is 0.76 V. In this regard, the oxidation-reductionpotential is a value with respect to a standard hydrogen electrode at apH of 14 (at 25° C.). Accordingly, a treatment liquid according to thepresent invention containing a hypobromite ion, hypochlorite ion, orozone oxidizes Br⁻ into a hypobromite ion, whereby the concentration ofthe hypobromite ion in the treatment liquid can be kept high, thusmaking it possible to stabilize the etching rate of ruthenium.

An example in which a hypochlorite ion is used as an oxidizing agent isshown in Table 8. The Table shows that, at any pH, theoxidation-reduction potential of the hypochlorite ion/Cl⁻ system ishigher than that of the hypobromite ion/Br⁻ system. As above-mentioned,the treatment liquid according to the present invention containing botha hypobromite ion and a hypochlorite ion lengthens the stability time ofthe etching rate of ruthenium, and thus, can be particularly suitablyutilized. In contrast, use of an oxidizing agent which has a weakoxidative power in alkali, for example, hydrogen peroxide, does not makeit possible to oxidize Br⁻ into a hypochlorite ion efficiently, andthus, results in a low etching rate of ruthenium.

The concentration of the hypochlorite ion in a treatment liquidaccording to the present invention is not limited to any value as longas the value does not depart from the object of the present invention,and the concentration is preferably 0.1 mass % or more and 10 mass % orless. The concentration of hypochlorite ion which is less than 0.1 mass% is unable to oxidize Br⁻ efficiently, resulting in decreasing theetching rate of ruthenium. In addition, the hypochlorite ion added in anamount of more than 10 mass % decreases the stability of thehypochlorite ion, and thus, is not suitable. The concentration of theoxidizing agent is more preferably 0.3 mass % or more and 7 mass % orless, most preferably 0.5 mass % or more and 4 mass % or less, in termsof satisfying both the inhibition of RuO₄ gas and the etching rate ofruthenium.

In addition, a higher proportion of a hypochlorite ion to a hypobromiteion causes the reaction between the hypochlorite ion and the hypobromiteion to promote a reaction for forming a bromic acid ion, and thus,decreases the hypobromite ion concentration.

The concentration of ozone in a treatment liquid according to thepresent invention is not limited to any value as long as the value doesnot depart from the object of the present invention, and theconcentration is preferably 0.1 mass ppm or more and 1000 mass ppm (0.1mass %) or less. The concentration of less than 0.1 mass ppm causes Br⁻to be oxidized into a hypobromite ion at a low rate, and thus, does notaffect the etching rate of ruthenium. In addition, the ozoneconcentration is more preferably 1 mass ppm or more and 500 mass ppm orless, in terms of dissolving ozone in the treatment liquid stably.Furthermore, the ozone concentration of 5 mass ppm or more and 200 massppm or less makes it possible to oxidize Br⁻ into a hypobromite ionefficiently, and is particularly preferable. In addition, any widelyknown method can be used, without any problem, as a method of generatingozone and a method of dissolving ozone in a treatment liquid. Forexample, electric discharge in a gas containing oxygen generates ozone,and the gas containing ozone is brought in contact with the treatmentliquid, thus causing part or all of the ozone to be dissolved in thetreatment liquid, whereby a treatment liquid containing ozone can beformed. Ozone may be brought in contact with a treatment liquidcontinuously or intermittently. Bringing ozone in contact with atreatment liquid before etching of ruthenium is started makes itpossible that the treatment liquid undergoes a smaller decrease in theconcentration of BrO⁻ and achieves a stable etching rate. In cases whereozone is brought in contact with a treatment liquid which has etchedruthenium, in other words, a treatment liquid containing RuO₄, RuO₄ ⁻,RuO₄ ²⁻, or the like, bringing ozone, little by little, in contact witha treatment liquid intermittently can prevent an increase in thegeneration of RuO₄ gas.

The above-mentioned method of generating a hypochlorite ion is notlimited to any particular method, and a hypochlorite ion generated byany method can be suitably used for a treatment liquid according to thepresent invention. Examples of methods which can be suitably used togenerate a hypochlorite ion include adding hypochlorite, spargingchlorine gas, and the like. Among these, a method in which hypochloriteis added to a treatment liquid is more suitable because the methodallows the concentration of a hypochlorite ion to be easily controlled,and allows the hypochlorite to be easily handled. Examples of such ahypochlorite include tetraalkylammonium hypochlorite, sodiumhypochlorite, potassium hypochlorite, calcium hypochlorite, magnesiumhypochlorite, and hypochlorous acid. Among these, tetraalkylammoniumhypochlorite or hypochlorous acid is particularly suitable in terms ofcontaining no metal which is problematic in semiconductor production,and tetraalkylammonium hypochlorite is most suitable in terms of beingable to be present stably at a high concentration.

Suitable examples of the tetraalkylammonium hypochlorite include atetraalkylammonium hypochlorite containing a tetraalkylammonium ionhaving 1 to 20 carbon number per alkyl group. Specific examples thereofinclude tetramethylammonium hypochlorite, tetraethylammoniumhypochlorite, tetrapropylammonium hypochlorite, tetrabutylammoniumhypochlorite, tetrapentylammonium hypochlorite, and tetrahexylammoniumhypochlorite; and tetramethylammonium hypochlorite andtetraethylammonium hypochlorite are more suitable in terms of havingmore hypochlorite ions per unit weight. Tetramethylammonium hypochloriteis easily available in the form of a high purity product, and thus, ismost suitable.

A method of producing the tetramethylammonium hypochlorite is notlimited to any particular method, and the tetramethylammoniumhypochlorite produced by a widely known method can be used. For example,a tetramethylammonium hypochlorite which can be suitably used isproduced by: a method in which chlorine is sparged intotetramethylammonium hydroxide; a method in which hypochlorous acid andtetramethylammonium hydroxide are mixed; a method in which an ionexchange resin is used to replace a cation in a hypochlorite solutionwith tetramethylammonium; a method in which a distillate of a solutioncontaining hypochlorite and tetramethylammonium hydroxide are mixed; andthe like.

In cases where a treatment liquid according to the present inventioncontains both a hypochlorite ion or ozone and Br⁻, whether ahypochlorite ion or ozone continuously oxidizes Br⁻ into BrO⁻ depends onthe quantitative ratio between the hypochlorite ion and Br⁻ contained inthe treatment liquid or the quantitative ratio between the ozone and Br⁻contained in the treatment liquid. In cases where the molarconcentration of Br⁻ present in the treatment liquid is higher than themolar concentration of a hypochlorite ion or ozone, all the amount ofBr⁻ cannot be oxidized into BrO⁻. The molar concentration of ahypochlorite ion or ozone in the treatment liquid according to thepresent invention is preferably higher than the molar concentration ofBr⁻. In cases where Br⁻ is oxidized into BrO⁻ by passing a gaseousoxidizing agent such as ozone through a treatment liquid, the totalnumber of moles of the gaseous oxidizing agent to be passed is desirablymore than the number of moles of Br⁻ contained in the treatment liquid.

Examples of methods of producing a hypobromite ion in a treatment liquidinclude a method in which a bromine-containing compound is oxidized byan oxidizing agent. The quantitative ratio between a bromine-containingcompound and an oxidizing agent contained in the treatment liquid ispreferably determined taking into consideration the stoichiometric ratioand reaction rate at which the bromine-containing compound and theoxidizing agent react to generate a hypobromite ion and thestoichiometric ratio and reaction rate at which Br⁻ and the oxidizingagent contained in the treatment liquid react to generate a hypobromiteion, but in reality, a plurality of factors complicatedly affect oneanother in these reactions, and thus, it is difficult to determine asuitable quantitative ratio of the bromine-containing compound to theoxidizing agent. However, if the ratio of a value obtained by dividingthe concentration of the bromine-containing compound by the chemicalequivalent (molar equivalent) of the bromine-containing compound to avalue obtained by dividing the concentration of the oxidizing agent bythe chemical equivalent (molar equivalent) of the oxidizing agent is inthe range of from 0.001 to 100, not only BrO⁻ can be efficientlygenerated from the bromine-containing compound by the oxidizing agentbut also Br⁻ generated by the reduction reaction or decompositionreaction of BrO⁻ can be reoxidized into BrO⁻, and thus, the etching rateof ruthenium is stabilized.

For example, in cases where the bromine-containing compound istetramethylammonium bromide and where the oxidizing agent istetramethylammonium hypochlorite, the chemical equivalent (molarequivalent) of the bromine-containing compound and the chemicalequivalent (molar equivalent) of the oxidizing agent are equal in thereaction between these chemical species, and thus, it is only necessarythat the ratio of the molar concentration of the bromine-containingcompound to the concentration of the oxidizing agent is in the range offrom 0.001 to 100.

The quantitative ratio between a hypobromite ion and a hypochlorite ioncontained in the treatment liquid is preferably determined taking intoconsideration the decrease rate of the hypobromite ion: to be moreaccurate, the rate at which Br⁻ is generated by the reduction reactionand/or decomposition reaction of the hypobromite ion; and the rate ofthe reaction in which Br⁻ is oxidized into BrO⁻ by the hypochlorite ion.In reality, however, a plurality of factors complicatedly affect oneanother in these reactions, and thus, it is difficult to determine asuitable quantitative ratio between the hypobromite ion and thehypochlorite ion. However, if the ratio of the molar concentration ofthe hypobromite ion to the molar concentration of the hypochlorite ion(the molar concentration of the hypobromite ion/the molar concentrationof the hypochlorite ion) is in the range of from 0.001 to 100, Br⁻generated by the reduction reaction or decomposition reaction of BrO⁻can be reoxidized into BrO⁻ by the hypochlorite ion, and thus, theetching rate of ruthenium is stabilized.

In the present invention, the treatment liquid for a semiconductor withruthenium preferably has a pH of 8 or more and 14 or less. The treatmentliquid having a pH of 8 or more and 14 or less makes it possible to etchruthenium efficiently, stabilizes the etching rate of ruthenium, andfurthermore, can be hopefully expected to decrease the generation amountof RuO₄ gas. The lower the pH, the higher the etching rate of ruthenium;but the lower the pH, the more the generation amount of RuO₄ gas.Accordingly, in treating a semiconductor wafer containing ruthenium, itis extremely important to select a pH which can satisfy both the etchingrate and the inhibition of RuO₄ gas. From this viewpoint, a treatmentliquid for a semiconductor with ruthenium in the present invention morepreferably has a pH of 12 or more and 14 or less, still more preferably12 or more and less than 13. Causing the treatment liquid to have a pHof 12 or more and less than 13 makes it possible to etch ruthenium at asufficient rate and furthermore inhibit the generation of RuO₄ gas. Thetreatment liquid having a pH of less than 8 tends more to generate RuO₂particles.

Ruthenium contained in a semiconductor wafer for which a treatmentliquid according to the present invention is used may be formed by anymethod. To form a film of ruthenium, a method widely known insemiconductor production processes, for example, CVD, ALD, PVD,sputtering, or the like can be utilized. In the present invention,ruthenium refers to a ruthenium metal or a ruthenium alloy.

In the present invention, a “ruthenium metal” refers not only to a metalruthenium but also to a ruthenium metal containing 70 at. % or more ofruthenium, to an oxide (RuOx), nitride (RuN), or oxynitride (RuNO) ofruthenium, and to the like. As used herein, an oxide of ruthenium refersto ruthenium dioxide or diruthenium trioxide (trihydrate). In addition,a “ruthenium alloy” in the present invention refers to an alloycontaining 70 at. % or more and 99.99 at. % or less of ruthenium andcontaining a metal which is other than ruthenium and whose concentrationis higher than the concentration at which the metal is containedinevitably. In the present invention, a ruthenium metal and a rutheniumalloy are each described as ruthenium when it is not necessary toparticularly distinguish them.

A ruthenium alloy may contain any metal besides ruthenium; examples of ametal contained in a ruthenium alloy include tantalum, silicon, copper,hafnium, zirconium, aluminum, vanadium, cobalt, nickel, manganese, gold,rhodium, palladium, titanium, tungsten, molybdenum, platinum, iridium,and the like; and the ruthenium alloy may contain an oxide, nitride, orsilicide of any of these metals.

These rutheniums may be intermetallic compounds, ionic compounds, orcomplexes. In addition, ruthenium may be exposed on the surface of awafer, or covered by another metal, metal oxide film, insulation film,resist, or the like. Even in cases where ruthenium is covered by anothermaterial, the RuO₄ gas generation inhibition effect is achieved when theruthenium is brought in contact with a treatment liquid according to thepresent invention and caused to dissolve. Furthermore, if the rutheniumis not caused to dissolve actively, in other words, if the ruthenium istreated as an object of protection, a treatment liquid according to thepresent invention makes it possible to inhibit RuO₄ gas generated fromthe very slightly dissolved ruthenium.

For example, in a ruthenium wiring formation step, a treatment liquidaccording to the present invention is used as below-mentioned. First, asubstrate composed of a semiconductor (for example, Si) is provided. Theprovided substrate is oxidized to form a silicon oxide film on thesubstrate. Then, an interlayer insulation film composed of a lowdielectric constant (Low-k) film is formed, and viaholes are formed atpredetermined intervals. After the viaholes are formed, ruthenium isembedded in the viaholes by thermal CVD to further form a rutheniumfilm. This ruthenium film is etched using a treatment liquid accordingto the present invention, and is thereby planarized while the generationof RuO₄ gas is inhibited. This makes it possible to form highly reliableruthenium wiring in which RuO₂ particles are inhibited.

Another aspect of a treatment liquid according to the present inventionis a treatment liquid containing at least a bromine-containing compound,an oxidizing agent, a basic compound, and water. The stepwisedescription follows below.

(Bromine-Containing Compound)

A bromine-containing compound to be used in a treatment liquid accordingto the present invention may be any compound, provided that the compoundcontains a bromine atom, and is oxidized by the below-mentionedoxidizing agent to generate bromine, a hypobromous acid, hypobromiteion, bromous acid, bromous acid ion, bromic acid, bromic acid ion,perbromic acid, perbromic acid ion, or bromide ion. Examples ofcompounds to be preferably used include at least one selected from thegroup consisting of a bromine salt and hydrogen bromide. As used herein,hydrogen bromide may be hydrogen bromide gas or hydrobromic acid whichis an aqueous solution of hydrogen bromide. Examples of bromine saltsinclude lithium bromide, sodium bromide, potassium bromide, rubidiumbromide, cesium bromide, ammonium bromide, onium bromides, and the like.As used herein, an onium bromide refers to a compound formed of an oniumion and a bromide ion. An onium ion is a polyatomic cation compoundformed by adding excessive protons (hydrogen cations) to a monoatomicanion. Specific examples thereof include cations such as an imidazoliumion, pyrrolidinium ion, pyridinium ion, piperidinium ion, ammonium ion,phosphonium ion, fluoronium ion, chloronium ion, bromonium ion, iodoniumion, oxonium ion, sulfonium ion, selenonium ion, telluronium ion,arsonium ion, stibonium ion, bismuthonium ion, and the like. Inaddition, a compound which generates hypobromous acid or a hypobromiteion in the treatment liquid can be suitably used as a bromine-containingcompound. Examples of such compounds include, but are not limited to,bromohydantoins, bromoisocyanuric acids, bromosulfamic acids,bromochloramines, and the like. More specific examples of the compoundsinclude 1-bromo-3-chloro-5,5-dimethylhydantoin,1,3-dibromo-5,5-dimethylhydantoin, tribromoisocyanuric acid, and thelike.

The bromine-containing compound may be in the form of hydrogen bromideor bromine salt when being added to the treatment liquid, may be in theform of a solution containing bromine salt when being added to thetreatment liquid, or may be in the form of bromine gas when being addedto the treatment liquid. To be easily handled in semiconductorproduction processes, the bromine-containing compound is preferably inthe form of bromine salt, a solution containing bromine salt, orhydrogen bromide when being mixed with another treatment liquid. Thetreatment liquid may contain one kind of bromine-containing compound ora combination of two or more kinds thereof.

In semiconductor production, contamination by metal or a metal ioncauses a decrease in the yield rate, and thus, the bromine-containingcompound desirably contains no metal. Bromine gases, hydrogen bromide,and onium bromides among bromine salts contain substantially no metal,and thus, can be suitably used as bromine-containing compounds in thepresent invention. Among onium bromides, a quaternary onium bromide, atertiary onium bromide, and hydrogen bromide are industrially availableand easy to handle, and thus, are more suitable as bromine-containingcompounds in the present invention.

A quaternary onium bromide is a bromine salt composed of an ammonium ionor a phosphonium ion which can be stably present in the treatmentliquid. Examples of quaternary onium bromides includetetramethylammonium bromide, tetraethylammonium bromide,tetrapropylammonium bromide, tetrabutylammonium bromide,tetrapentylammonium bromide, tetrahexylammonium bromide,methyltriethylammonium bromide, diethyldimethylammonium bromide,trimethylpropylammonium bromide, butyltrimethylammonium bromide,trimethylnonylammonium bromide, decyltrimethylammonium bromide,tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide,trimethylstearylammonium bromide, decamethonium bromide,phenyltrimethylammonium bromide, benzyltrimethylammonium bromide,dimethylpyrrolidinium bromide, dimethylpiperidinium bromide,1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylpyridinium bromide,and the like. In addition, a compound in which a proton is added to atertiary amine, secondary amine, or primary amine can be used as abromine-containing compound. Examples of bromine-containing compoundsinclude methylamine hydrobromide, dimethylamine hydrobromide, ethylaminehydrobromide, diethylamine hydrobromide, triethylamine hydrobromide,2-bromoethylamine hydrobromide, 2-bromoethyldiethylamine hydrobromicacid, ethylenediamine dihydrobromide, propylamine hydrobromide,butylamine hydrobromide, tert-butylamine hydrobromide, neopentylaminehydrobromide, 3-bromo-1-propylamine hydrobromide, dodecylaminehydrobromide, cyclohexaneamine hydrobromide, benzylamine hydrobromide,and the like. Examples of quaternary phosphonium bromides includetetramethylphosphonium bromide, tetraethylphosphonium bromide,tetrapropylphosphonium bromide, tetrabutylphosphonium bromide,tetraphenylphosphonium bromide, methyltriphenylphosphonium bromide,phenyltrimethylphosphonium bromide,methoxycarbonylmethyl(triphenyl)phosphonium bromide, and the like. Atertiary onium bromide is a bromine salt composed of a sulfonium ionwhich can be stably present in the treatment liquid. Examples oftertiary sulfonium bromides include trimethylsulfonium bromide,triethylsulfonium bromide, tripropylsulfonium bromide, tributylsulfoniumbromide, triphenylsulfonium bromide, and(2-carboxyethyl)dimethylsulfonium bromide. Among these, a quaternaryonium bromide, which is a bromine salt composed of an ammonium ion, ispreferable because a quaternary onium bromide has high stability, isindustrially available in the form of a high purity product, and isinexpensive.

The quaternary onium bromide is preferably tetraalkylammonium bromidewhich has excellent stability in particular and can be easilysynthesized.

In the tetraalkylammonium bromide, the carbon number of each alkyl groupis not limited to any particular value, and the carbon numbers of thefour alkyl groups may be the same or different. Examples of such analkylammonium bromide which can be suitably used include atetraalkylammonium bromide having 1 to 20 carbon numbers per alkylgroup. Among these, tetraalkylammonium bromide in which the alkyl grouphas a smaller carbon number can be more suitably used because of havingmore bromine atoms per weight. Examples thereof includetetramethylammonium bromide, tetraethylammonium bromide,tetrapropylammonium bromide, tetrabutylammonium bromide,tetrapentylammonium bromide, tetrahexylammonium bromide, and the like;tetramethylammonium bromide, tetraethylammonium bromide,tetrapropylammonium bromide, and tetrabutylammonium bromide aresuitable; and tetramethylammonium bromide is most suitable. Thetreatment liquid may contain one or more kinds of bromine-containingcompounds.

A tetraalkylammonium bromide to be used in the present invention may bea commercially available tetraalkylammonium bromide, or may be atetraalkylammonium bromide produced from a tetraalkylammonium ion and abromide ion. A method of producing a tetraalkylammonium bromide onlyneeds to include mixing an aqueous solution containingtetraalkylammonium hydroxide with an aqueous solution containing abromide ion or with a bromine-containing gas which is dissolved in waterto generate a bromide ion, examples of such a gas including hydrogenbromide.

Examples of the tetraalkylammonium hydroxide to be used to producetetraalkylammonium bromide include tetramethylammonium hydroxide,tetraethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide, and the like. Among these, thetetraalkylammonium hydroxide is more preferably tetramethylammoniumhydroxide in terms of the large number of hydroxide ions per unit weightand in terms of being easily available in the form of a high purityproduct.

Examples of bromine ion sources which generate a bromide ion to be usedto produce tetraalkylammonium bromide include hydrogen bromide, lithiumbromide, sodium bromide, potassium bromide, rubidium bromide, cesiumbromide, ammonium bromide, and the like. Among these, hydrogen bromideis suitable in terms of containing substantially no metal, beingindustrially available, and being easily available in the form of a highpurity product.

The addition amount of the bromine-containing compound is not limited toany particular value, and can be determined taking into considerationthe etching rate of ruthenium, the stability of the treatment liquid,the solubility of the bromine-containing compound, cost, and the like.The bromine-containing compound added to the treatment liquid isoxidized by the below-mentioned oxidizing agent to become a chemicalspecies effective for etching of ruthenium, specific examples of such achemical species including bromine (Br₂), hypobromous acid (HBrO), ahypobromite ion (BrO⁻), bromous acid (HBrO₂), bromous acid ion (BrO₂ ⁻),bromic acid (HBrO₃), bromic acid ion (BrO₃ ⁻), perbromic acid (HBrO₄),perbromic acid ion (BrO₄ ⁻), and bromide ion (Br⁻).

Among the above-mentioned chemical species effective for etching ofruthenium, the treatment liquid containing HBrO, BrO⁻, HBrO₂, BrO₂ ⁻,HBrO₃, and BrO₃ ⁻ allows the etching rate of ruthenium to be high, andthus, the treatment liquid preferably contains these chemical species.Among these, the treatment liquid containing a larger amount of HBrO andBrO⁻ (hereinafter referred to as BrO⁻ or the like) allows the etchingrate of ruthenium to be particularly high, and thus, is more preferablein terms of being able to shorten the treatment time.

Accordingly, in cases where the bromine-containing compound is oxidizedby an oxidizing agent, the bromine atom contained in thebromine-containing compound is preferably oxidized into HBrO, BrO⁻,HBrO₂, BrO₂ ⁻, HBrO₃, or BrO₃ ⁻, and more preferably oxidized into BrO⁻or the like among these.

Increasing the proportion of BrO⁻ or the like contained in the treatmentliquid makes it possible to increase the etching rate of ruthenium.Specifically, a treatment liquid in which the proportion of BrO⁻ in 1mol of bromine element contained in the treatment liquid is more than0.5 mol enables ruthenium to be etched efficiently.

In cases where Br⁻ is generated by the decomposition of theabove-mentioned chemical species effective for etching of ruthenium, inother words, Br₂, HBrO, BrO⁻, HBrO₂, BrO₂ ⁻, HBrO₃, BrO₃ ⁻, HBrO₄, orBrO₄ ⁻, or by the reaction between ruthenium and the chemical species,it is preferable that the treatment liquid contains an oxidizing agentwhich can oxidize Br⁻ back into the chemical species effective foretching of ruthenium. Having such an oxidizing agent present in thetreatment liquid enables the concentration of the chemical specieseffective for etching of ruthenium to be kept high and makes it possibleto maintain the etching rate of ruthenium. In cases where BrO⁻ or thelike is decomposed by disproportionation, HBrO₃ or BrO₃ ⁻ and Br⁻ aregenerated via HBrO₂ or BrO₂ ⁻ in some cases. Even in cases where atreatment liquid according to the present invention contains one or moreof HBrO₂, BrO₂ ⁻, HBrO₃, BrO₃ ⁻, Br⁻, and the like in addition to BrO⁻or the like, the treatment liquid can be suitably used for etching ofruthenium. Also in cases where the treatment liquid contains a pluralityof chemical species effective for etching of ruthenium, it is preferablethat the treatment liquid contains an oxidizing agent which can oxidizeBr⁻ back into a chemical species effective for etching of ruthenium.

In addition, in cases where the treatment liquid contains not only BrO⁻but also a decomposition product of BrO⁻ (for example, HBrO₂, BrO₂ ⁻,HBrO₃, BrO₃ ⁻, Br⁻, or the like), a change in the concentration of BrO⁻in the treatment liquid is moderate, stabilizing the etching rate ofruthenium. Accordingly, a treatment liquid according to the presentinvention may contain one or more kinds of the above-mentioneddecomposition products of BrO⁻. A treatment liquid according to thepresent invention containing, for example, BrO⁻ or BrO₃ ⁻ can besuitably used for etching of ruthenium.

To etch ruthenium efficiently, the proportion of BrO⁻ in 1 mol ofbromine element contained in the treatment liquid is preferably morethan 0.5 mol.

Both the oxidization of a bromine-containing compound or Br⁻ into achemical species effective for etching of ruthenium and etching ofruthenium are carried out in an alkaline treatment liquid, which canthus become a treatment liquid in which the proportion of BrO⁻ in 1 molof bromine element contained in the treatment liquid is more than 0.5mol. This is because the bromine-containing compound or Br⁻ in thealkaline treatment liquid is directly oxidized by an oxidizing agentinto BrO⁻ or the like.

A treatment liquid having an alkaline pH makes it possible that theoxidization of Br⁻ by an oxidizing agent and etching ruthenium arecarried out repeatedly and continuously. In other words, the followingreactions are repeated: (A) a reaction in which an oxidizing agentoxidizes Br⁻ into a chemical species effective for etching of ruthenium;and (B) a reaction in which the chemical species effective for etchingof ruthenium etches ruthenium, thus reverting to Br⁻. Owing to this, theproportion of BrO⁻ in 1 mol of bromine element in the treatment liquidis more than 0.5 mol, enabling ruthenium to be etched efficiently.

Furthermore, the reactions (A) and (B) induced repeatedly andcontinuously result in causing the concentration of BrO⁻ or the like inthe treatment liquid to be kept constant, thus stabilizing the etchingrate of ruthenium.

The progress of (A) the reaction in which an oxidizing agent oxidizesBr⁻ into a chemical species effective for etching of ruthenium causesthe oxidizing agent in the treatment liquid to be consumed. When all theoxidizing agent in the treatment liquid is consumed for the reaction, nomore bromine-containing compound or Br⁻ is oxidized. However, atreatment liquid in which the amount of a chemical species effective foretching of ruthenium is large, in other words, a treatment liquid inwhich the proportion of BrO⁻ in 1 mol of bromine element is more than0.5 mol does not lose the ruthenium etching capability immediately, andmakes it possible that ruthenium is etched until the chemical specieseffective for etching of ruthenium in the treatment liquid is no morepresent.

In cases where a bromine-containing compound or Br⁻ is oxidized into achemical species effective for etching of ruthenium in an acidictreatment liquid, the bromine-containing compound or Br⁻ is oxidized byan oxidizing agent to generate bromine gas. The bromine gas absorbed byalkali generates hypobromite and a bromine salt at a molar ratio of 1to 1. Accordingly, the proportion of BrO⁻ contained in the treatmentliquid results in 0.5 mol per mole of bromine element contained in thetreatment liquid, and is never more than 0.5. Obviously, in cases whereall the amount of the bromine-containing compound or Br⁻ contained inthe treatment liquid is not oxidized, the proportion of BrO⁻ containedin the treatment liquid results in less than 0.5 per mole of bromineelement contained in the treatment liquid.

In cases where the bromine-containing compound or Br⁻ is oxidized into achemical species effective for etching of ruthenium under acidicconditions and where ruthenium is etched under alkaline conditions, thetime for generating bromine gas and the time for adjusting the pH of thetreatment liquid are required between the generation of the chemicalspecies effective for etching of ruthenium by the oxidizing agent andthe etching of ruthenium, thus causing the ruthenium etching process tobe intermittent and markedly lowering the productivity. Because of this,the generation of the chemical species effective for etching ofruthenium by the oxidizing agent under acidic conditions has to becarried out only once before the etching of ruthenium. In this case, theabove-mentioned reactions (A) and (B) are not induced repeatedly andcontinuously, and thus, the proportion of BrO⁻ in 1 mol of bromineelement contained in the treatment liquid is 0.5 or less.

Using the treatment liquid for etching of ruthenium causes the chemicalspecies effective for etching of ruthenium to react with ruthenium,causing a decrease only on the part of the species, and thus, theproportion of BrO⁻ in 1 mol of bromine element contained in thetreatment liquid is still less than 0.5.

The treatment liquid in which the proportion of BrO⁻ in 1 mol of bromineelement contained in the treatment liquid is 0.5 mol or less issignificantly lower in the stability of the etching rate of ruthenium,the number of ruthenium films that can be etched, and the life time ofthe treatment liquid than the treatment liquid in which the proportionof BrO⁻ in 1 mol of bromine element contained in the treatment liquid ismore than 0.5 mol. Accordingly, to etch ruthenium stably andefficiently, it is preferable that the treatment liquid is alkaline, andthat the proportion of BrO⁻ in 1 mol of bromine element contained in thetreatment liquid is more than 0.5 mol.

With respect to the total mass of the treatment liquid, the additionamount of the bromine-containing compound is preferably 0.008 mass % ormore and less than 10 mass % as a bromine element content. The amount ofless than 0.008 mass % causes ruthenium to be etched at a low rate, andis not very practicable. The amount of 10 mass % or more makes itdifficult to control the etching rate of ruthenium in productionprocesses. Accordingly, the addition amount of the bromine-containingcompound contained in a treatment liquid according to the presentinvention is preferably 0.008 mass % or more and less than 10 mass % asa bromine element content in terms of achieving a high etching rate andcarrying out an efficient production with the etching rate controlled.In addition, the upper limit of the addition amount of thebromine-containing compound contained in a treatment liquid according tothe present invention is more preferably less than 2 mass % as a bromineelement content. Less than 2.0 mass % as the addition amount of thebromine-containing compound makes it more unlikely to induce thedisproportionation of the chemical species effective for etching ofruthenium, particularly HBrO, BrO⁻, HBrO₂, and BrO₂ ⁻ and makes itpossible to inhibit fluctuations in the concentrations of these chemicalspecies, thus stabilizing the etching rate. Furthermore, less than 2.0mass % as the addition amount of the bromine-containing compound makesit possible that control of the etching rate of ruthenium causes theconcentration of RuO₄ gas generated per unit time to be controlled at alow level, and that the generation of RuO₂ particles is furtherdecreased.

In addition, the lower limit of the addition amount of thebromine-containing compound contained in a treatment liquid according tothe present invention is more preferably 0.01 mass % or more as abromine element content. The bromine-containing compound in an additionamount of 0.01 mass % or more makes it possible that the chemicalspecies effective for etching of ruthenium is generated efficiently,that the etching rate is still higher, and that the ruthenium is etchedefficiently at a stable etching rate. Accordingly, the addition amountof the bromine-containing compound contained in a treatment liquidaccording to the present invention is still more preferably 0.01 mass %or more and less than 2 mass % as a bromine element content. Inaddition, the addition amount of the bromine-containing compound isstill more preferably 0.04 mass % or more and less than 2.0 mass % as abromine element content in terms of increasing the throughput andenhancing the production efficiency. Furthermore, the addition amount ofthe bromine-containing compound is most preferably 0.08 mass % or moreand less than 2.0 mass % as a bromine element content in that theetching rate is more stabilized because the oxidizing agent makes itmore likely to induce reoxidization into a chemical species effectivefor etching of ruthenium.

The pH of a solution containing the bromine-containing compound is notlimited to any particular value, and is preferably pH 8 or more and 14or less, more preferably 12 or more and 13 or less. A solution having apH in these range makes it possible to decrease a pH decrease arisingfrom mixing a solution containing the below-mentioned oxidizing agentand a solution containing the bromine-containing compound, and makes itpossible to produce, store, and use a treatment liquid according to thepresent invention in a stable manner. To cause a solution containing thebromine-containing compound to have a pH of less than 8, the pH andliquid amount of the solution containing the bromine-containing compoundcan be adjusted so that a treatment liquid obtained after mixing thesolution containing the below-mentioned oxidizing agent and the solutioncontaining the bromine-containing compound can have an alkaline pH.

An iodine-containing compound can be used in the same manner as thebromine-containing compound. In this case, iodine contained in theiodine-containing compound can be oxidized by an oxidizing agentcontained in the treatment liquid to become a chemical species foretching of ruthenium.

(Oxidizing Agent)

An oxidizing agent to be used for a treatment liquid according to thepresent invention has a function which can oxidize thebromine-containing compound to generate a chemical species effective foretching of ruthenium. Specific examples thereof include nitric acid,sulfuric acid, persulfuric acid, peroxodisulfuric acid, hypochlorousacid, chlorous acid, chloric acid, perchloric acid, hypobromous acid,bromous acid, bromic acid, perbromic acid, hypoiodous acid, iodous acid,iodic acid, periodic acid, salts thereof, ions generated fromdissociation of these salts, hydrogen peroxide, ozone, fluorine,chlorine, bromine, iodine, permanganate, chromate, dichromate, ceriumsalt, and the like. These oxidizing agents may be used singly or incombination of two or more thereof. In cases where any of theseoxidizing agents is added to a treatment liquid according to the presentinvention, the oxidizing agent can be selected in the form of anysuitable one of a solid, liquid, and gas in accordance with theproperties of the oxidizing agent to be used.

In terms of being able to be stably present despite of being alkaline,preferable oxidizing agents among these are hypochlorous acid, chlorousacid, chloric acid, perchloric acid, hypobromous acid, bromous acid,bromic acid, perbromic acid, hypoiodous acid, iodous acid, iodic acid,periodic acid, salts thereof, ions generated from dissociation of thesesalts, ozone, and hydrogen peroxide; more preferable oxidizing agentsare hypochlorous acid, chlorous acid, chloric acid, perchloric acid,hypobromous acid, bromous acid, bromic acid, perbromic acid, saltsthereof, ions generated from dissociation of these salts, ozone, andhydrogen peroxide; still more preferable oxidizing agents arehypochlorite ions and ozone; and most preferable oxidizing agents arehypochlorite ions.

Using hypochlorous acid, tetraalkylammonium hypochlorite, which is asalt thereof, or ozone as the oxidizing agent makes it possible tosubstantially prevent contamination by metal, and thus, is suitable fora treatment liquid for semiconductor production. Among these,tetraalkylammonium hypochlorite is stable in alkali, can oxidize thebromine-containing compound efficiently, and thus is particularlysuitable.

The oxidizing agent is not limited to any particular concentration, andcan be added in an amount which makes it possible to oxidize thebromine-containing compound into a chemical species effective foretching of ruthenium.

The addition amount of the oxidizing agent is preferably 0.1 mass ppm ormore and 10 mass % or less. The oxidizing agent the addition amount ofwhich is less than 0.1 mass ppm is unable to oxidize thebromine-containing compound efficiently, resulting in decreasing theetching rate of ruthenium. In other words, a composition in which theoxidizing agent is not mixed causes the etching rate to be low. Inaddition, the oxidizing agent added in an amount of more than 10 mass %decreases the stability of the oxidizing agent, and thus, is notsuitable. The concentration of the oxidizing agent is more preferably0.1 mass % or more and 10 mass % or less, still more preferably 0.3 mass% or more and 7 mass % or less, most preferably 0.5 mass % or more and 4mass % or less, in terms of satisfying both the inhibition of RuO₄ gasand the etching rate of ruthenium. In this regard, the oxidizing agentwhich is ozone preferably has a concentration within above mentionedranges.

The pH of a solution containing the oxidizing agent is not limited toany particular value, and is preferably pH 8 or more and 14 or less,more preferably 12 or more and 13 or less. A solution having a pH inthese ranges makes it possible to decrease a pH decrease arising frommixing a solution containing the bromine-containing compound and asolution containing the oxidizing agent, and makes it possible toproduce, store, and use a treatment liquid according to the presentinvention in a stable manner. To cause a solution containing theoxidizing agent to have a pH of less than 8, the pH and liquid amount ofthe solution containing the oxidizing agent can be adjusted so that atreatment liquid obtained after mixing the solution containing thebromine-containing compound and the solution containing the oxidizingagent can have an alkaline pH.

<Method of Producing Tetraalkylammonium Hypochlorite Solution>

As above-mentioned, an oxidizing agent which may be contained in atreatment liquid according to the present invention is preferablytetraalkylammonium hypochlorite. Accordingly, a preferable aspect of amethod of producing tetraalkylammonium hypochlorite will be describedbelow. The method of producing the oxidizing agent includes apreparation step of providing a tetraalkylammonium hydroxide solutionand a reaction step of contacting the tetraalkylammonium hydroxidesolution with chlorine.

(Preparation Step of Providing Tetraalkylammonium Hydroxide Solution)

A tetraalkylammonium hydroxide solution usually contains carbon dioxide,which is derived from the air. The carbon dioxide is present in the formof carbonate ions or bicarbonate ions in the solution. The concentrationof carbon dioxide is not limited to any particular value, and ispreferably 0.001 ppm or more and 500 ppm or less (by mass), morepreferably 0.005 ppm or more and 300 ppm or less, still more preferably0.01 ppm or more and 100 ppm or less, in terms of carbonate ions.Causing the tetraalkylammonium hydroxide solution to have a carbondioxide concentration of 0.001 ppm or more and 500 ppm or less makes itpossible to inhibit a change in the pH of the obtainedtetraalkylammonium hypochlorite solution. As a result, the storagestability of the tetraalkylammonium hypochlorite solution can beenhanced.

In the present embodiment, the tetraalkylammonium hydroxide solution ispreferably a solution of a tetraalkylammonium hydroxide in which thealkyl group has 1 to 10 carbon numbers, more preferably a solution oftetraalkylammonium hydroxide in which the alkyl group has 1 to 5 carbonnumbers. Specific examples of tetraalkylammonium hydroxides includetetramethylammonium hydroxide, tetraethylammonium hydroxide,tetrabutylammonium hydroxide, and the like. These tetraalkylammoniumhydroxides may be used singly or in combination of two or more kindsthereof. In addition, the carbon numbers of the four alkyl groupscontained in the tetraalkylammonium hydroxide may be same or different.

(Reaction Step of Contacting Tetraalkylammonium Hydroxide Solution withChlorine)

Allowing a tetraalkylammonium hydroxide solution to contact and reactwith chlorine causes the hydroxide ion of the tetraalkylammoniumhydroxide to be replaced with a hypochlorite ion generated by chlorine,thus generating a tetraalkylammonium hypochlorite solution.

In the present embodiment, the upper limit of the concentration ofcarbon dioxide in the gas phase portion is 100 vol ppm, and theconcentration of 0.001 to 100 vol ppm, preferably 0.01 to 80 vol ppm,makes it possible to sufficiently control the pH of thetetraalkylammonium hypochlorite solution and to produce atetraalkylammonium hypochlorite solution having excellent storagestability.

The range of the pH of the liquid phase portion in the reaction stepaccording to the present embodiment is 10.5 or more. The upper limit isnot limited to any particular value, and an excessively high pH duringreaction can cause the hypochlorite ion to be decomposed and decreasethe effective chlorine concentration during long-time storage carriedout at the same pH after completion of the reaction. Accordingly, the pHof the liquid phase portion in the reaction step is preferably less than14, more preferably less than 13.9, still more preferably 11 or more andless than 13.8. The pH in these ranges allows the decomposition of thehypochlorite ion to be inhibited during the storage of the obtainedtetraalkylammonium hypochlorite solution, enhancing the storagestability.

In the present embodiment, the range of the reaction temperature of thetetraalkylammonium hydroxide solution in the reaction step is preferably−35° C. or more and 25° C. or less, more preferably −15° C. or more and25° C. or less, still more preferably 0° C. or more and 25° C. or less.The reaction temperature in these ranges makes it possible that thetetraalkylammonium hydroxide solution and chlorine react sufficiently toobtain a tetraalkylammonium hypochlorite solution at a high generationefficiency.

As clear from the above description, a tetraalkylammonium hypochloritesolution obtained by the production method according to the presentembodiment has excellent storage stability, and thus, can be suitablyused as an oxidizing agent to be contained in a treatment liquidaccording to the present invention.

(Basic Compound)

A basic compound to be used for a treatment liquid according to thepresent invention is not limited to any particular compound, andexamples of basic compounds to be used include lithium hydroxide, sodiumhydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide,magnesium hydroxide, calcium hydroxide, strontium hydroxide, bariumhydroxide, ammonia, choline, alkylammonium hydroxide, and the like.Among these basic compounds, sodium hydroxide, potassium hydroxide,ammonia, choline, and alkylammonium hydroxide are easily available,afford a high ruthenium etching rate when used for the treatment liquid,and are suitable. Ammonia, choline, and alkylammonium hydroxide containno metal, and thus, can be particularly suitably used for a treatmentliquid according to the present invention. Examples of industriallyavailable alkylammonium hydroxides include tetramethylammoniumhydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide, and the like, and tetramethylammoniumhydroxide is most suitable in terms of being easily available in theform of a high purity product of semiconductor fabrication grade. Thebasic compound can be added in the form of a solid or an aqueoussolution to the treatment liquid.

The concentration of the basic compound is not limited to any particularvalue as long as the value does not depart from the object of thepresent invention, and the solution containing the basic compoundpreferably has a pH in the range of 8 or more and 14 or less, morepreferably 12 or more and 13 or less. Allowing the pH of the solutioncontaining the basic compound to be in these pH ranges makes it possibleto decrease a pH decrease arising from mixing a solution containing theabove-mentioned oxidizing agent and a solution containing thebromine-containing compound, and makes it possible to produce, store,and use a treatment liquid according to the present invention in astable manner.

(Water)

Water contained in a treatment liquid according to the present inventionis preferably water which is made free from metal ions, organicimpurities, and particles by any one of distillation, ion exchange,filtration, and various kinds of adsorption treatments, and the water isparticularly preferably pure water or ultrapure water. Such water can beobtained by a known method widely utilized for semiconductor production.

(pH)

A treatment liquid according to the present invention preferably has apH of 8 or more and 14 or less. The treatment liquid having a pH in thisrange makes it possible to etch ruthenium at a sufficient rate andinhibit the generation of RuO₄ gas. The treatment liquid having a pH ofless than 8 causes RuO₂ particles to be generated markedly and decreasesthe yield rate of semiconductor elements. In addition, the treatmentliquid having a pH of more than 14 causes the above-mentioned oxidizingagent to be decomposed, and thus, will undesirably not allow thebromine-containing compound to be constantly oxidized. This means thatthe etching rate of ruthenium is not constant, complicates the processcontrol in semiconductor production processes, and thus, needs to beavoided.

The higher the pH of the treatment liquid, the smaller the amount ofRuO₄ gas generated by the etching of ruthenium. In addition, the higherthe pH of the treatment liquid, the lower the etching rate of ruthenium.Thus, the treatment liquid preferably has a pH of 12 or more and 14 orless, more preferably 12 or more and less than 13, in terms ofsatisfying both the inhibition of RuO₄ gas and the etching rate. Thetreatment liquid having a pH in these ranges enables that chemicalspecies effective for etching of ruthenium which is contained in atreatment liquid according to the present invention to dissolveruthenium at a sufficient etching rate, and inhibits the generation ofRuO₄ gas.

The pH for etching of ruthenium metal is preferably 11 or more and 14 orless, more preferably 12 or more and less than 13. The treatment liquidhaving a pH in these ranges makes it possible that the etching rate anda decrease in the generation amount of RuO₄ gas are satisfied in etchingof ruthenium metal.

The pH for etching of ruthenium alloy preferably is 12 or more and 14 orless, more preferably 12 or more and less than 13.

(Method of Producing Treatment Liquid)

In cases where a treatment liquid according to the present inventioncontains a bromine-containing compound, an oxidizing agent, a basiccompound, and water, the treatment liquid may be a one-component liquidor a two- or more multi-component solution. In cases where the treatmentliquid is a one-component liquid, the liquid is a solution containingall of a bromine-containing compound, an oxidizing agent, a basiccompound, and water. In cases where the treatment liquid is atwo-component or more multi-component liquid, the treatment liquid maybe produced by mixing the liquid components. In cases where thetreatment liquid is a two- or more multi-component liquid, each liquidcomponent contains at least one of a bromine-containing compound, anoxidizing agent, a basic compound, and water. The treatment liquid mayfurther contain the below-mentioned other component(s). Whether thetreatment liquid is a one-component liquid or a two- or moremulti-component liquid, having a bromine-containing compound, anoxidizing agent, and a basic compound coexisting in the treatment liquidcauses the bromine-containing compound to be oxidized by the oxidizingagent to generate a chemical species effective for etching of ruthenium.

In cases where a plurality of treatment liquids are used, the liquidsare preferably separated into a treatment liquid(s) containing abromine-containing compound and a treatment liquid(s) containing anoxidizing agent. Separating the bromine-containing compound and theoxidizing agent prevents the bromine-containing compound from beingoxidized by the oxidizing agent, and makes it possible to stably storethe treatment liquid according to the present invention.

A method which can be used to mix treatment liquids is a method widelyknown as a method of mixing chemical liquids for semiconductors.Examples of methods which can be suitably used include: a method inwhich a mixing tank is used; a method in which liquids are mixed in thepiping of a semiconductor production apparatus (in-line mixing); amethod in which a plurality of liquids are simultaneously sprayed onto awafer so as to be mixed; and the like.

In cases where a plurality of separated treatment liquids are mixed toproduce a treatment liquid, the separated treatment liquids may be mixedany time. In cases where the oxidization of the bromine-containingcompound takes some time, mixing the treatment liquids before etchingruthenium makes it possible to provide the time to generate a chemicalspecies effective for etching of ruthenium. In this case, taking time tooxidize the bromine-containing compound results in a bottleneck inproduction lines, and thus, causes a decrease in throughput in somecases. For this reason, the shorter the time taken by the oxidization,the better, and the time is preferably one hour or less. The time takenby the oxidization of the bromine-containing compound can be controlledby suitably selecting the concentration of the oxidizing agent, theconcentration of the bromine-containing compound, the pH of thetreatment liquid, the temperature of the treatment liquid, a method ofstirring the treatment liquid, and the like. For example, in cases wherea hypobromite ion is generated by using an oxidizing agent to oxidize abromine-containing compound, increasing the concentration of thereactant enables the time taken by the oxidization to be shortenedaccording to reaction kinetics. In this case, the concentrations of boththe oxidizing agent and the bromine-containing compound may beincreased, or the concentration of only one of them may be increased.Increasing the temperature of the treatment liquid during mixing alsoenables the time taken by the oxidization of the bromine-containingcompound to be shortened.

In addition, a low concentration of the chemical species effective foretching of ruthenium causes the life time of the treatment liquid to beshort, and conceivably makes it difficult to control the productionprocesses. In such a case, the mixing is preferably carried outimmediately before the ruthenium etching is carried out.

Accordingly, in cases where a plurality of treatment liquids are mixed,it is preferable to mix a solution containing an oxidizing agent and abasic compound and a solution containing a bromine-containing compound,it is more preferable to mix a solution containing a hypochlorite ionand a basic compound and a solution containing a bromine-containingcompound. The solution containing a hypochlorite ion and a basiccompound is preferably alkaline. For mixing, it is preferable that thebromine-containing compound is added to the solution containing anoxidizing agent and a basic compound. This is because, for example, incases where the oxidizing agent is an alkali solution containinghypochlorous acid and where the solution containing a bromine-containingcompound is an acidic solution, adding the former to the lattergradually causes the hypochlorous acid to be decomposed in the acidicsolution and thus, will undesirably generate chlorine gas, which istoxic. The solution containing a basic compound and an oxidizing agentand the solution containing a bromine-containing compound may each beeither a solution or an aqueous solution, but, in cases where thesolvent is other than water, for example, an organic or inorganicsolvent, the solvent will undesirably react with the oxidizing agent,which is thus decomposed. For this reason, the solution is preferably anaqueous solution.

In mixing a treatment liquid according to the present invention, thetreatment liquid after mixing preferably has an alkaline pH.Specifically, the treatment liquid preferably has a pH of 8 or more and14 or less. In cases where the treatment liquid before mixing has a pHof less than 8, the concentration(s) of the basic compound and/or wateris/are adjusted so that the treatment liquid (containing abromine-containing compound, an oxidizing agent, a basic compound, andwater) after mixing can have a pH of 8 or more and 14 or less. Causingthe pH of the treatment liquid after mixing to be maintained at 8 ormore and 14 or less in such a manner allows the oxidizing agent topromptly change the bromine-containing compound to a chemical specieseffective for etching of ruthenium, thus enabling a ruthenium film to beetched at a stable and sufficient rate.

In cases where a plurality of treatment liquids are mixed to generate achemical species effective for etching of ruthenium, the treatmentliquids to be mixed may have the same or different pH(s). In cases wherethe treatment liquids have the same pH, the pH of the treatment liquidafter mixing does not change significantly, and thus, the treatmentliquid can be suitably used as an etching liquid for ruthenium.

In cases where a plurality of treatment liquids are mixed to generate achemical species effective for etching of ruthenium, the composition(the concentration of the bromine-containing compound, the concentrationof the oxidizing agent, the concentration of the basic compound, and thepH) after mixing only needs to be within the above-mentioned ranges, anda mixing method including a mixing ratio, a mixing order, and the likefor the treatment liquids to be mixed is not limited to any particularmethod. For example, however, in cases where an alkali solutioncontaining a hypochlorous acid compound and an acidic solutioncontaining a bromine-containing compound are mixed, local decompositionof the hypochlorous acid compound will undesirably be promoted, andthus, in this case, it is preferable that the acidic solution containinga bromine-containing compound is added to and mixed with the alkalisolution containing a hypochlorous acid compound.

In the present invention, a hypochlorous acid compound refers to acompound which generates a hypochlorous acid or a hypochlorite ion inthe treatment liquid. Examples of the hypochlorous acid compoundsinclude hypochlorous acid, hypochlorite, hydantoins, isocyanuric acids,sulfamic acids, chloramines, and the like. Among these, hypochlorousacid and hypochlorite are preferable because these can generatehypochlorous acid or a hypochlorite ion efficiently. The hypochlorousacid is preferably tetraalkylammonium hypochlorite, and is morepreferably tetramethylammonium hypochlorite in particular because thiscontains hypochlorous acid or a hypochlorite ion in a large amount perunit weight.

Those chemical species effective for etching of ruthenium which aregenerated by causing a bromine-containing compound to be oxidized by anoxidizing agent vary depending on the pH, oxidation-reduction potential(ORP), and the like of the treatment liquid, and are mainly bromine, abromide ion, hypobromous acid, bromous acid, bromic acid, perbromicacid, and ions thereof.

In addition, a treatment liquid according to the present inventionpreferably contains metal, specifically, sodium, potassium, aluminum,magnesium, iron, nickel, copper, silver, cadmium, and lead, each in anamount of 1 ppb or less.

A treatment liquid according to the present invention and thebromine-containing compound, an oxidizing agent, a basic compound,water, solvent, and the other additives used for the treatment liquidpreferably contain smaller amounts of ammonia and amines. This isbecause ammonia and amines present in the treatment liquid react withthe oxidizing agent, the bromine-containing compound, those chemicalspecies effective for etching of ruthenium which are generated from thebromine-containing compound, and the like decrease the stability of thetreatment liquid. For example, in cases where tetramethylammoniumhydroxide is used as a basic compound, ammonia and amines, particularlytrimethyl amine, contained in the basic compound cause the stability ofthe treatment liquid to decrease in some cases. Because of this, incases where tetramethylammonium hydroxide is used for a treatment liquidaccording to the present invention, the total amount of amines containedin the basic compound is preferably 100 ppm or less. The amines in atotal amount of 100 ppm or less have a minor influence caused byreaction with the oxidizing agent, the bromine-containing compound, andthose chemical species effective for etching of ruthenium which aregenerated from the bromine-containing compound, and such amines do notimpair the stability of the treatment liquid.

A treatment liquid according to the present invention is preferablyproduced under light-shielding to prevent light from decomposing theoxidizing agent, those chemical species effective for etching ofruthenium which are generated form the bromine-containing compound, andthe like.

In the production of a treatment liquid according to the presentinvention, it is also preferable to prevent carbon dioxide fromdissolving into the treatment liquid. In cases where a treatment liquidaccording to the present invention is alkaline, carbon dioxide easilydissolves into the treatment liquid, and can cause a change in the pH. Achange in the pH of the treatment liquid not only constitutes a factorfor varying the etching rate of ruthenium but also decreases thestability the treatment liquid. The dissolution of carbon dioxide intothe treatment liquid can be decreased by a method, for example, passingan inert gas flow through a production apparatus to purge carbon dioxidetherefrom, causing a reaction under an inert gas atmosphere, and thelike. Having 100 ppm or less carbon dioxide in the production apparatusenables the influence caused by the dissolution of carbon dioxide to benegligible.

In the production of a treatment liquid according to the presentinvention, that face of a reaction container which is in contact withthe treatment liquid is preferably formed of glass or an organic polymermaterial. This is because the reaction container having the inner faceformed of glass or an organic polymer material makes it possible tofurther decrease contamination by impurities such as metal, metal oxide,organic substances, and the like. Examples of organic polymer materialswhich can be used for the inner face of the reaction container includevinyl chloride resins (soft and hard vinyl chloride resins), nylonresins, silicone resins, polyolefin resins (polyethylene andpolypropylene), fluorine resins, and the like. Among these, fluorineresins are preferable, considering the easiness of molding, solventresistance, less elution of impurities, and the like. The fluorine resinis not limited to any particular material provided that the resin is aresin (polymer) containing a fluorine atom, and, as this resin, a knownfluorine resin can be used. Examples thereof includepolytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidenefluoride, tetrafluoroethylene-hexafluoropropylene copolymers,tetrafluoroethylene-perfluoroalkylvinylether copolymers,tetrafluoroethylene-ethylene copolymers,chlorotrifluoroethylene-ethylene copolymers, cyclized polymers ofperfluoro(butenylvinylether), and the like.

(Other Additives)

If desired, another additive to be conventionally used for a treatmentliquid for a semiconductor may be blended with a treatment liquidaccording to the present invention to the extent that such blending doesnot impair the object of the present invention. Examples of otheradditives which can be added include acids, metal corrosion preventionagents, water-soluble organic solvents, fluorine compounds, oxidizingagents, reducing agents, complexing agents, chelators, surfactants,defoaming agents, pH adjustors, stabilizers, and the like. Theseadditives may be added singly or in combination of two or more thereof.

A treatment liquid according to the present invention may contain analkali metal ion, an alkaline earth metal ion, and the like which arederived from these additives or which are to be added for theconvenience in the production of the treatment liquid. For example, thetreatment liquid may contain a sodium ion, potassium ion, calcium ion,or the like. If remaining on a semiconductor wafer, however, such analkali metal ion, alkaline earth metal ion, or the like has an adverseeffect (an adverse effect such as a decrease in the yield rate ofsemiconductor wafers) on a semiconductor element; and thus, the less theamount of such an ion or the like, the more preferable; and in reality,the nearer zero without limit the amount, the more preferable. Becauseof this, it is preferable that, for example, the pH adjustor is neitheran alkali metal hydroxide such as sodium hydroxide or an alkaline earthmetal hydroxide but an organic alkali such as ammonia, amine, choline,or tetraalkylammonium hydroxide.

Specifically, the total amount of an alkali metal ion and an alkalineearth metal ion is preferably 1 mass % or less, more preferably 0.7 mass% or less, still more preferably 0.3 mass % or less, particularlypreferably 10 ppm or less, most preferably 500 ppb or less.

A treatment liquid according to the present invention may furthercontain an organic solvent. A treatment liquid according to the presentinvention containing an organic solvent makes it possible to inhibit thegeneration of RuO₄ gas. The organic solvent to be used may be anysolvent provided that the solvent does not impair the function of atreatment liquid according to the present invention. Examples of organicsolvents include, but are obviously not limited to, sulfolane,acetonitrile, carbon tetrachloride, 1,4-dioxane, and the like.

A temperature at which ruthenium is etched with a treatment liquidaccording to the present invention is not limited to any particularvalue, and can be determined taking into consideration the etching rateof ruthenium, the stability of the treatment liquid, the generationamount of RuO₄ gas, and the like. The higher the treatment temperature,the more the generation amount of RuO₄ gas; and thus, the lower thetreatment temperature, the more preferable. In addition, the higher thetemperature, the higher the etching rate of ruthenium. A temperature atwhich ruthenium is etched is preferably 10° C. to 90° C., morepreferably 15° C. to 70° C., most preferably 20° C. to 60° C., in termsof satisfying both the inhibition of RuO₄ gas and the etching rate ofruthenium.

A period of treatment time for which ruthenium is etched with atreatment liquid according to the present invention is in the range offrom 0.1 to 120 minutes, preferably 0.3 to 60 minutes, and can besuitably selected in accordance with the etching conditions and thesemiconductor element to be used. An organic solvent such as alcohol canbe used as a rinsing liquid after a treatment liquid according to thepresent invention is used, and using deionized water alone for rinsingis sufficient.

Use of a treatment liquid according to the present invention makes itpossible to inhibit the generation of RuO₄ gas and remove, at asufficient etching rate (10 Å/min or more), ruthenium sticking to theend face portion and back face portion of a semiconductor wafer. Incases where an etching rate of 10 Å/min or more is needed, theconcentration of the hypobromite ion contained in the treatment liquid,the concentration of the hypochlorite ion contained therein, theconcentration of the bromine-containing compound contained therein, theconcentration of the oxidizing agent contained therein, the pH of thetreatment liquid, the treatment temperature, a method of contacting thetreatment liquid with a wafer, and the like can be suitably selected.

After the above-mentioned treatment liquid according to the presentinvention is produced, the treatment liquid can be used to etch aruthenium metal film and/or ruthenium alloy film deposited on asubstrate.

(Storage of Treatment Liquid)

A treatment liquid according to the present invention is preferablystored at low temperature and/or under light-shielding. Storage at lowtemperature and/or under light-shielding can be hopefully expected tohave an effect which inhibits the decomposition of an oxidizing agent,hypobromite ion, and the like in the treatment liquid. Furthermore,storing the treatment liquid in a container filled with inert gas andthus preventing contamination by carbon dioxide enables the stability ofthe treatment liquid to be maintained. In addition, the inner face ofthe container, in other words, the face in contact with the treatmentliquid is preferably formed of glass or an organic polymer material.This is because the reaction container having the inner face formed ofglass or an organic polymer material makes it possible to furtherdecrease contamination by impurities such as metal, metal oxide, organicsubstances, and the like. Examples of organic polymer materials whichcan be suitably used for the inner face of the reaction containerinclude materials exemplified with reference to the production of atreatment liquid according to the present invention. In addition, the pHof the treatment liquid during storage can be suitably selected, and toprevent the decomposition of the hypobromite ion, the bromine-containingcompound, the oxidizing agent, the other additive(s), and the like, thepH of the treatment liquid is preferably alkaline, more preferably 8 ormore and 14 or less, most preferably 12 or more and 14 or less.

Example

Below, the present invention will be described more specifically withreference to Examples, but the present invention is not limited to theseExamples.

(Method of Measuring pH)

The pH of 10 mL of treatment liquid prepared in each of Examples andComparative Examples was measured using a tabletop pH meter (LAQUA F-73;manufactured by Horiba, Ltd.). The pH was measured after each treatmentliquid was prepared and stabilized at 25° C.

(Formation of Ruthenium Film and Amount of Change in Film Thickness)

A ruthenium film used in each of Examples and Comparative Examples wasformed as below-mentioned. An oxide film was formed on a silicon waferusing a batch type thermal oxidization furnace, and a ruthenium film,1200 Å (±10%), was formed on the oxide film by sputtering. A four-proberesistivity meter (Loresta-GP; manufactured by Mitsubishi ChemicalAnalytech Co., Ltd.) was used to measure the sheet resistance, and themeasurement was converted to a film thickness, which was regarded as thethickness of the ruthenium film before etching treatment. After theetching treatment, the four-probe resistivity meter was used to measurethe sheet resistance in the same manner, and the measurement wasconverted to a film thickness, which was regarded as the thickness ofthe ruthenium film after etching treatment. A difference between theruthenium film thickness after etching treatment and the ruthenium filmthickness before etching treatment was regarded as the amount of changein film thickness between before and after etching treatment.

(Formation of Ruthenium Dioxide Film and Amount of Change in FilmThickness)

A ruthenium dioxide film used in each of Examples was formed asbelow-mentioned. An oxide film was formed on a silicon wafer using thebatch type thermal oxidization furnace, and a ruthenium dioxide film,1000 Å (±10%), was formed on the oxide film by sputtering. Thefour-probe resistivity meter (Loresta-GP; manufactured by MitsubishiChemical Analytech Co., Ltd.) was used to measure the sheet resistance,and the measurement was converted to a film thickness, which wasregarded as the thickness of the ruthenium dioxide film before etchingtreatment. After the etching treatment, the four-probe resistivity meterwas used to measure the sheet resistance in the same manner, and themeasurement was converted to a film thickness, which was regarded as thethickness of the ruthenium dioxide film after etching treatment. Adifference between the ruthenium dioxide film thickness after etchingtreatment and the ruthenium dioxide film thickness before etchingtreatment was regarded as the amount of change in film thickness betweenbefore and after etching treatment.

(Method of Calculating Etching Rate of Ruthenium or Ruthenium Dioxide)

The treatment liquid in each of Examples and Comparative Examples wasprovided in amount of 60 mL in a fluorine resin-made container with alid (a PFA container, 94.0 mL; manufactured by As One Corporation).Etching treatment of ruthenium or ruthenium dioxide was carried out byimmersing each sample piece, 10×20 mm, in the treatment liquid at 25° C.for one minute.

In addition, 60 mL of the treatment liquid was provided in a fluorineresin-made container with a lid; the container was immersed for one hourin a water bath (Isotemp water bath with a general-purpose hood;manufactured by Thermo Fisher Scientific Inc.) heated to 60° C.; and thetreatment liquid temperature was kept at 60° C. The etching treatment ofruthenium or ruthenium dioxide was carried out by immersing each samplepiece, 10×20 mm, in the treatment liquid at 60° C. for one minute.

A value was calculated as an etching rate by dividing the amount ofchange in film thickness between before and after etching treatment bythe immersion time, and evaluated as an etching rate in the presentinvention. The treatment temperatures and treatment times are listed inTable 5. A film which exhibited less than 5 Angstrom as the amount ofchange in film thickness between before and after treatment was regardedas unetched.

(Quantitative Analysis of RuO₄ Gas)

The generation amount of RuO₄ gas was measured by ICP-OES. Into ahermetically sealed container, 5 mL of the treatment liquid was added,and one Si wafer, 10×20 mm, on which a ruthenium film having a thicknessof 1200 Å was formed was immersed in the liquid at 25° C. or 60° C.until all ruthenium was dissolved. Then, an air flow was passed throughthe hermetically sealed container, and the gas phase in the hermeticallysealed container was sparged into the absorbing liquid (1 mol/L, NaOH)in a container to cause the RuO₄ gas generated during the immersion tobe trapped in the absorbing liquid. The amount of ruthenium in thisabsorbing liquid was measured by ICP-OES to determine the amount of Ruin the generated RuO₄ gas. Whether all ruthenium on the Si waferimmersed in the treatment liquid was dissolved was verified by using thefour-probe resistivity meter (Loresta-GP; manufactured by MitsubishiChemical Analytech Co., Ltd.) to measure the sheet resistances beforeand after immersion, which were converted to film thicknesses. A valueobtained by dividing the weight of Ru contained in the RuO₄ gas-absorbedliquid by the area of the wafer with Ru was used to evaluate thegeneration amount of RuO₄ gas. The RuO₄ gas generation amount of 40μg/cm² or less was regarded as meaning that the generation of RuO₄ gaswas inhibited.

Table 1 to Table 4 show the compositions of the treatment liquids, Table5 shows the evaluation results, Table 6 shows the preparation conditionsof the treatment liquids, Table 7 shows the production conditions of theoxidizing agents, Table 8 shows the oxidation-reduction potentials(calculated values) of the hypochlorite ion (ClO⁻)/Cl⁻ systems and thehypobromite ion (BrO⁻)/Br⁻ systems at 25° C., and Table 9 shows thepreparation conditions of the aqueous tetramethylammonium bromidesolution.

(Method of Calculating Concentrations of Hypobromite Ion andHypochlorite Ion)

The concentrations of a hypobromite ion and a hypochlorite ion weremeasured using an ultraviolet and visible spectrophotometer (UV-2600;manufactured by Shimadzu Corporation). An aqueous solution of ahypobromite ion and a hypochlorite ion each having a known concentrationwas used to prepare a calibration curve to determine the concentrationsof the hypobromite ion and the hypochlorite ion in the producedtreatment liquid. The concentration of the hypobromite ion wasdetermined from the measurement data obtained when the absorptionspectrum was stabilized after the bromine-containing compound, theoxidizing agent, and the basic compound were mixed.

Example 1

(Preparation of Sample for Etching)

The method described in (Formation of ruthenium film and amount ofchange in film thickness) was used to form a ruthenium film, and asample piece cut to 10×20 mm was used for evaluation.

(Production of Oxidizing Agent)

In a 2-L glass three-neck flask (manufactured by Cosmos Bead Co., Ltd.),209 g of aqueous 25 mass % tetramethylammonium hydroxide solution and791 g of ultrapure water were mixed to obtain an aqueous 5.2 mass %tetramethylammonium hydroxide solution containing CO₂ in an amount of0.5 ppm. This solution had a pH of 13.8.

Then, a stirring bar (30 mm in full length×8 mm in diameter;manufactured by As One Corporation) was put in the three-neck flask;through one opening, a thermometer protecting tube (a bottom-sealedtype; manufactured by Cosmos Bead Co., Ltd.) and a thermometer wereinserted; through another opening, a tip of a PFA-made tube (F-8011-02;manufactured by Flon Industry Co., Ltd.) was immersed in the bottom ofthe solution, wherein the tube was connected to a chlorine gas cylinderand a nitrogen gas cylinder so as to be freely switchable betweenchlorine gas and nitrogen gas; and the other opening was connected to agas washing bottle (a gas washing bottle, Model Number 2450/500;manufactured by As One Corporation) filled with an aqueous 5 mass %sodium hydroxide solution. Then, a flow of nitrogen gas having a carbondioxide concentration of less than 1 ppm was passed through the PFA-madtube at 0.289 Pa·m³/second (as converted at 0° C.) for 20 minutes topurge carbon dioxide from the gas phase portion. When this took place,the carbon dioxide concentration of the gas phase portion was 1 ppm orless.

Then, a magnetic stirrer (C-MAG HS10; manufactured by As OneCorporation) was placed in the lower portion of the three-neck flask,and rotated at 300 rpm for stirring; chlorine gas (having a specifiedpurity of 99.4%; manufactured by Fujiox Co., Ltd.) was supplied at 0.059Pa·m³/second (as converted at 0° C.) for 180 minutes while the peripheryof the three-neck flask was cooled with ice water; and a solutionmixture of an aqueous tetramethylammonium hypochlorite solution (anoxidizing agent; corresponding to 3.51 mass %, 0.28 mol/L) andtetramethylammonium hydroxide (corresponding to 0.09 mass %, 0.0097mol/L) was thus obtained. When this took place, the liquid temperatureduring the reaction was 11° C.

(Production of Treatment Liquid)

To 99.21 g of that solution mixture of an aqueous tetramethylammoniumhypochlorite solution and tetramethylammonium hydroxide which wasobtained by the above-mentioned operation, 0.79 g of 97 mass %tetramethylammonium bromide (manufactured by Tokyo Chemical IndustryCo., Ltd.) (corresponding to 0.77 mass %, 0.05 mol/L; 0.40 mass % as abromine element content) was added to obtain 100 g of treatment liquidas per each of the compositions listed in Table 1 to Table 4. Here,water listed in Table 3 refers to water containing tetramethylammoniumchloride in cases where the oxidizing agent is tetramethylammoniumhypochlorite.

(Evaluation)

Immediately after the treatment liquid was produced, the pH of thetreatment liquid, the etching rate of ruthenium, the generation amountof RuO₄ gas, and the concentration of a hypobromite ion were evaluated.The etching rate of ruthenium was evaluated in accordance with theabove-mentioned “Method of calculating etching rate of ruthenium”. Thegeneration amount of RuO₄ gas was evaluated in accordance with theabove-mentioned “Quantitative analysis of RuO₄ gas”. The concentrationof the hypobromite ion was evaluated in accordance with theabove-mentioned “Method of calculating concentration of hypobromiteion”. The stability of the etching rate was evaluated asbelow-mentioned. The etching rate of the produced treatment liquid wasevaluated every ten hours in accordance with the above-mentioned “Methodof calculating etching rate of ruthenium”. A period of time during whichan increase/decrease between the obtained etching rate and the etchingrate exhibited immediately after the production was within ±20% wasdefined as the stability time of the etching rate.

Examples 2 to 23 and Comparative Examples 1 to 3

The treatment liquid in each of Examples 2 to 23 and ComparativeExamples 1 to 3 was prepared in the same manner as in Example 1 so thatthe concentration of the bromine-containing compound, the concentrationof the oxidizing agent, the concentration of the basic compound, and thepH could be as per each of the compositions listed in Table 1 to Table4, and a ruthenium film (sample piece) provided in the same manner as inExample 1 was used for evaluation. In Comparative Examples 1 and 2, theamount of change in film thickness between before and after treatmentwas less than 5 Angstrom, and the Ru was regarded as unetched. Becauseof this, the RuO₄ gas was not evaluated. In each of Examples 19 and 22in which hydrobromic acid (acidic) used as a bromine-containing compoundwas mixed with an aqueous solution (alkaline) containing an oxidizingagent and a basic compound to prepare an aqueous solution (alkaline)containing a hypobromite ion, followed by etching of ruthenium, it waspossible to verify, in the same manner as in the other Examples, thatthe etching rate of ruthenium was high, that the stability of theetching rate was excellent, and that the RuO₄ gas inhibition effect washigh.

Example 24

(Preparation of Solution Containing Oxidizing Agent and Basic Compound)

A method of producing an oxidizing agent as described in Example 1 wasused to prepare a solution (A liquid) containing an oxidizing agent anda basic compound so that the concentration of the oxidizing agent, theconcentration of the basic compound, and the pH could be as per each ofthe compositions listed in Table 6.

(Preparation of Solution Containing Bromine-Containing Compound)

Tetramethylammonium bromide (manufactured by Tokyo Chemical IndustryCo., Ltd.) (97 mass %) in an amount of 3.97 g (corresponding to 3.85mass %, 0.25 mol/L), an aqueous tetramethylammonium hydroxide solution(25 mass %) in an amount of 0.354 g, and ultrapure water in an amount of95.6 g were mixed to prepare a solution (B liquid) containing abromine-containing compound so as to be as per each of the compositionslisted in Table 6.

(Production of Treatment Liquid)

To 80 g of the A liquid obtained by the above-mentioned operation, 20 gof the B liquid was added to obtain 100 g of treatment liquid as pereach of the compositions listed in Table 1 to Table 4.

(Evaluation)

The obtained treatment liquids were evaluated in the same manner as inExample 1.

Examples 25 to 30

In each of Examples 25 to 30, a treatment liquid was prepared in thesame manner as in Example 24 in accordance with the composition, mixingratio, and mixing method listed in Table 6 so that the concentration ofthe bromine-containing compound, the concentration of the oxidizingagent, the concentration of the basic compound, and the pH could be asper each of the compositions in Table 1 to Table 4; and the treatmentliquid was evaluated. The reaction time in Table 6 means the time takenuntil the etching rate was stabilized after the A liquid and the Bliquid were mixed, in other words, the time taken until theconcentration of the hypobromite ion (BrO⁻) was stabilized, or the timetaken until a change in the concentration of the hypobromite ion fellwithin ±5% as the concentration was measured every one minute.

Example 31

(Production of Treatment Liquid)

To 94.43 g of ultrapure water, 1.14 g of orthoperiodic acid(manufactured by Fujifilm Wako Pure Chemical Corporation) (correspondingto 1.14 mass %, 0.05 mol/L) and 0.79 g of tetramethylammonium bromide(manufactured by Tokyo Chemical Industry Co., Ltd., 97 mass %)(corresponding to 0.77 mass %, 0.05 mol/L) were added; the resultingmixture was left to stand for three hours; to the mixture, an aqueous 25mass % tetramethylammonium hydroxide solution was added until the pH ofthe resulting mixture became 11; and 100 g of treatment liquid as pereach of the compositions listed in Table 1 to Table 4 was thus obtained.

(Evaluation)

The obtained treatment liquids were evaluated in the same manner as inExample 1.

Example 32

(Production of Treatment Liquid)

To 78.21 g of ultrapure water, 0.79 g of tetramethylammonium bromide(manufactured by Tokyo Chemical Industry Co., Ltd., 97 mass %)(corresponding to 0.77 mass %, 0.05 mol/L) and 16.0 g of aqueous 25 mass% tetramethylammonium hydroxide solution were added, followed by adding5.0 g of orthoperiodic acid (manufactured by Fujifilm Wako Pure ChemicalCorporation) (corresponding to 5.0 mass %, 0.22 mol/L), to obtain 100 gof treatment liquid as per each of the compositions listed in Table 1 toTable 4.

(Evaluation)

The obtained treatment liquids were evaluated in the same manner as inExample 1.

Examples 33 to 35

In each of Examples 33 to 35, an oxidizing agent was produced in thesame manner as in Example 1 under the conditions listed in Table 7, anda treatment liquid was prepared in the same manner as in Example 1 sothat the concentration of the bromine-containing compound, theconcentration of the oxidizing agent, the concentration of the basiccompound, and the pH could be as per each of the compositions listed inTable 1 to Table 4. The treatment liquids were evaluated in the samemanner as in Example 1.

Example 36

(Production of Tetramethylammonium Bromide)

Ultrapure water in an amount of 90.88 g was added to an aqueous 25%tetramethylammonium hydroxide solution (manufactured by Fujifilm WakoPure Chemical Corporation) in an amount of 9.12 g to prepare an aqueous2.28% tetramethylammonium hydroxide solution. Then, 95.7 g of ultrapurewater was added to 4.3 g of 47% hydrobromic acid (manufactured by TokyoChemical Industry Co., Ltd.) to prepare 2.02% hydrobromic acid. Anaqueous 2.28% tetramethylammonium hydroxide solution in an amount of 50g and 2.02% hydrobromic acid in an amount of 50 g were mixed to obtain100 g of aqueous tetramethylammonium bromide solution listed in Table 9.

(Production of Treatment Liquid)

To 80 g of that solution mixture of an aqueous tetramethylammoniumhypochlorite solution and tetramethylammonium hydroxide which wasobtained in the same manner as in Example 1, 20 g of aqueous 3.85%tetramethylammonium bromide solution was added to obtain 100 g oftreatment liquid as per each of the compositions listed in Table 1 toTable 4.

(Evaluation)

The obtained treatment liquids were evaluated in the same manner as inExample 1.

Example 37

A treatment liquid as per each of the compositions listed in Table 1 toTable 4 was obtained in the same manner as in Example 3. Immediatelyafter the treatment liquid was produced, the pH of the treatment liquid,the etching rate of ruthenium dioxide, the generation amount of RuO₄gas, and the concentration of a hypobromite ion were evaluated. Theetching rate of ruthenium dioxide was evaluated in accordance with theabove-mentioned “Method of calculating etching rate of rutheniumdioxide”. The generation amount of RuO₄ gas was evaluated in accordancewith the above-mentioned “Quantitative analysis of RuO₄ gas”. Theconcentration of the hypobromite ion was evaluated in accordance withthe above-mentioned “Method of calculating concentration of hypobromiteion”. The stability of the etching rate was evaluated asbelow-mentioned. The etching rate of the produced treatment liquid wasevaluated every ten hours in accordance with the above-mentioned “Methodof calculating etching rate of ruthenium dioxide”. A period of timeduring which an increase/decrease between the obtained etching rate andthe etching rate exhibited immediately after the production was within±20% was defined as the stability time of the etching rate.

Example 38

A treatment liquid having a pH of 12, containing 0.075 g (0.05 mol/L) ofbromic acid sodium (manufactured by Fujifilm Wako Pure ChemicalCorporation), and containing the bromine-containing compound, theoxidizing agent, and the basic compound each having the sameconcentration as in Example 1 as listed in Table 1, was prepared. Theobtained treatment liquids were evaluated in the same manner as inExample 1.

Example 39

A treatment liquid having a pH of 12, containing 0.075 g (0.05 mol/L) ofbromic acid sodium (manufactured by Fujifilm Wako Pure ChemicalCorporation), and containing the bromine-containing compound, theoxidizing agent, and the basic compound each having the sameconcentration as in Example 10 as listed in Table 1, was prepared. Theobtained treatment liquids were evaluated in the same manner as inExample 1.

The compositions and evaluation results of the treatment liquids arelisted in Table 1 to Table 5. As shown in Table 5, ruthenium was notetched at all in Comparative Examples 1 and 2, and in ComparativeExample 3, in which etching was possible, the etching rate and stabilitywere low, and the generation amount of RuO₄ ⁻ gas was twice higher thanthe allowable value, making it possible to satisfy none of the etchingrate, stability, and RuO₄ ⁻ gas inhibition effect. In contrast, any ofthe treatment liquids in Examples affords a fast etching rate ofruthenium, excellent etching rate stability, and a high RuO₄ ⁻ gasinhibition effect, thus verifying that the treatment liquids satisfy theabove-mentioned three kinds of capability. As the results of Examples 24to 30, these treatment liquids have verified that the time taken untilthe etching rate is stabilized is within one hour, that is, sufficientlyshort. Example 37 provided a treatment liquid having the sameconcentration of hypobromite ion and the same pH as in Example 3, butmade it possible to verify that the treatment liquid had a high etchingcapability also for ruthenium dioxide. In each of Examples 38 and 39,the treatment liquid had BrO⁻, BrO₃ ⁻, and Br⁻ present therein, thusresulting in enhancing the stability of the etching rate.

TABLE 1 Bromine-containing compound Oxidizing agent Basic compoundExample 1 Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L) (3.51 mass %,0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 2 Tetramethylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(0.15 mass %, 0.01 mol/L) (3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097mol/L) Example 3 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (1.54 mass %, 0.1 mol/L)(3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 4Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L) (1.25 mass %,0.1 mol/L) (0.09 mass %, 0.0097 mol/L) Example 5 Tetramethylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(0.77 mass %, 0.05 mol/L) (3.51 mass %, 0.28 mol/L) (0.91 mass %, 0.0997mol/L) Example 6 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L)(3.51 mass %, 0.28 mol/L) (0.03 mass %, 0.0028 mol/L) Example 7Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L) (3.51 mass %,0.28 mol/L) (0.01 mass %, 0.00068 mol/L) Example 8 Tetrapropylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(2.66 mass %, 0.1 mol/L) (3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097mol/L) Example 9 Tetrapropylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (0.27 mass %, 0.01 mol/L)(3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 10Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (4.62 mass %, 0.3 mol/L) (3.51 mass %,0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 11 Tetramethylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(7.7 mass %, 0.5 mol/L) (3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097mol/L) Example 12 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L)(3.51 mass %, 0.28 mol/L) (0.27 mass %, 0.03 mol/L) Example 13Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (1.23 mass %, 0.08 mol/L) (1.13 mass %,0.09 mol/L) (0.63 mass %, 0.06 mol/L) Example 14 Tetramethylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(0.10 mass %, 0.006 mol/L) (3.51 mass %, 0.28 mol/L) (0.09 mass %,0.0097 mol/L) Example 15 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (0.39 mass %, 0.025 mol/L)(3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 16Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (2.70 mass %, 0.18 mol/L) (3.51 mass %,0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 17 Tetramethylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(0.77 mass %, 0.05 mol/L) (0.13 mass %, 0.01 mol/L) (0.09 mass %, 0.0097mol/L) Example 18 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L)(3.51 mass %, 0.28 mol/L) (2.87 mass %, 0.32 mol/L) Example 19 Hydrogenbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(0.4 mass %, 0.05 mol/L) (3.51 mass %, 0.28 mol/L) (0.73 mass %, 0.08mol/L) Example 20 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (0.15 mass %, 0.01 mol/L)(3.51 mass %, 0.28 mol/L) (0.91 mass %, 0.0997 mol/L)

TABLE 2 Bromine-containing compound Oxidizing agent Basic compoundExample 21 Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (0.02 mass %, 0.0013 mol/L) (1.25 mass %,0.10 mol/L) (0.09 mass %, 0.0097 mol/L) Example 22 Hydrogen bromideTetramethylammonium hypochlorite Tetramethylammonium hydroxide (1.62mass %, 0.2 mol/L) (3.51 mass %, 0.28 mol/L) (0.54 mass %, 0.2097 mol/L)Example 23 Trimethylsulfonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (0.4 mass %, 0.05 mol/L) (3.51 mass %,0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 24 Tetramethylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(0.77 mass %, 0.05 mol/L) (3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097mol/L) Example 25 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L)(3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 26Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L) (3.51 mass %,0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 27 Hydrogen bromideTetramethylammonium hypochlorite Tetramethylammonium hydroxide (0.4 mass%, 0.05 mol/L) (3.51 mass %, 0.28 mol/L) (0.56 mass %, 0.06 mol/L)Example 28 Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L) (3.51 mass %,0.28 mol/L) (0.27 mass %, 0.03 mol/L) Example 29 Tetramethylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(0.77 mass %, 0.05 mol/L) (3.51 mass %, 0.28 mol/L) (0.91 mass %, 0.0997mol/L) Example 30 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (3.85 mass %, 0.25 mol/L)(0.63 mass %, 0.05 mol/L) (0.91 mass %, 0.0997 mol/L) Example 31Tetramethylammonium bromide Orthoperiodic acid — (0.77 mass %, 0.05mol/L) (1.14 mass %, 0.05 mol/L) Example 32 Tetramethylammonium bromideOrthoperiodic acid Tetramethylammonium hydroxide (0.77 mass %, 0.05mol/L) (5.0 mass %, 0.22 mol/L) (4.0 mass %, 0.437 mol/L) Example 33Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L) (3.82 mass %,0.305 mol/L) (0.09 mass %, 0.0097 mol/L) Example 34 Tetramethylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(0.77 mass %, 0.05 mol/L) (3.82 mass %, 0.305 mol/L) (0.09 mass %,0.0097 mol/L) Example 35 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L)(5.01 mass %, 0.40 mol/L) (0.09 mass %, 0.0097 mol/L) Example 36Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L) (3.01 mass %,0.24 mol/L) (0.09 mass %, 0.0097 mol/L) Example 37 Tetramethylammoniumbromide Tetramethylammonium hypochlorite Tetramethylammonium hydroxide(1.54 mass %, 0.10 mol/L) (4.0 mass %, 0.32 mol/L) (0.09 mass %, 0.0097mol/L) Example 38 Tetramethylammonium bromide Tetramethylammoniumhypochlorite Tetramethylammonium hydroxide (0.77 mass %, 0.05 mol/L)(3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Example 39Tetramethylammonium bromide Tetramethylammonium hypochloriteTetramethylammonium hydroxide (4.62 mass %, 0.3 mol/L) (3.51 mass %,0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Comparative —Tetramethylammonium hypochlorite Tetramethylammonium hydroxide Example 1(3.51 mass %, 0.28 mol/L) (0.09 mass %, 0.0097 mol/L) Comparative —Tetramethylammonium hypochlorite Tetramethylammonium hydroxide Example 2(3.51 mass %, 0.28 mol/L) (0.91 mass %, 0.0997 mol/L) Comparative —Tetramethylammonium hypochlorite Tetramethylammonium hydroxide Example 3(3.51 mass %, 0.28 mol/L) (0.001 mass %, 0.000068 mol/L)

TABLE 3 Hypobromite Hypobromite ion/Bromine Water ion element [mass %]pH [mol/l] molar ratio Example 1 95.63 12 0.05 1 Example 2 96.25 12 0.011 Example 3 94.86 12 0.1 1 Example 4 97.89 12 0.05 1 Example 5 94.81 130.05 1 Example 6 95.69 11.5 0.05 1 Example 7 95.71 11 0.05 1 Example 893.74 12 0.1 1 Example 9 96.13 12 0.01 1 Example 10 91.78 12 0.28 0.93Example 11 88.70 12 0.28 0.56 Example 12 95.45 12.5 0.05 1 Example 1397.01 12.8 0.08 1 Example 14 96.30 12 0.006 1 Example 15 96.01 12 0.0251 Example 16 93.70 12 0.18 1 Example 17 99.71 12 0.01 0.2 Example 1892.85 13.5 0.05 1 Example 19 95.36 12.5 0.05 1 Example 20 95.43 13 0.0051

TABLE 4 Hypobromite Hypobromite ion/Bromine Water ion element [mass %]pH [mol/l] molar ratio Example 21 98.64 12 0.0013 1 Example 22 94.33 120.2 1 Example 23 96.00 12 0.05 1 Example 24 95.63 12 0.05 1 Example 2595.63 12 0.05 1 Example 26 95.63 12 0.05 1 Example 27 95.53 12 0.05 1Example 28 95.45 12.5 0.05 1 Example 29 94.81 13 0.05 1 Example 30 94.6113 0.05 0.2 Example 31 98.09 11 0.05 0.001 Example 32 90.23 11 0.050.0005 Example 33 95.32 12 0.05 1 Example 34 95.32 12 0.05 1 Example 3594.13 12 0.05 1 Example 36 96.13 12 0.05 1 Example 37 94.37 12 0.1 1Example 38 95.63 12 0.05 1 Example 39 91.78 12 0.28 0.93 Comparative96.40 12 — — Example 1 Comparative 95.58 13 — — Example 2 Comparative96.49 11 — — Example 3

TABLE 5 Treatment Treatment Etching temperature time rate Ru amountStability (° C.) (sec) (Å/min) [μg/cm²] [hours] Example 1 25 60 360 2.7160 Example 2 25 300 58 2.6 >200 Example 3 25 30 884 2.8 130 Example 425 60 278 2.8 110 Example 5 25 300 116 0 180 Example 6 25 30 2412 18 100Example 7 25 30 2534 30 80 Example 8 25 120 635 0 140 Example 9 25 30072 2.2 >200 Example 10 25 10 4263 2.7 30 Example 11 25 10 4083 2.7 30Example 12 25 300 171 1.0 170 Example 13 25 300 108 0 100 Example 14 25300 40 2.2 >200 Example 15 25 120 221 2.2 170 Example 16 25 30 1108 2.2110 Example 17 25 300 25 2.6 180 Example 18 25 300 40 0 >200 Example 1925 60 150 1.0 150 Example 20 60 60 50 1.3 50 Example 21 60 60 20 5.8 20Example 22 25 60 355 2.7 160 Example 23 25 60 270 2.5 45 Example 24 2560 356 2.6 162 Example 25 25 60 361 2.8 158 Example 26 25 60 359 2.8 161Example 27 25 60 358 2.7 160 Example 28 25 300 175 0.9 165 Example 29 25300 112 0.0 185 Example 30 25 300 75 0 >200 Example 31 25 300 85 31 95Example 32 25 300 25 29 >200 Example 33 25 60 361 2.7 172 Example 34 2560 362 2.6 171 Example 35 25 60 358 2.8 191 Example 36 25 60 350 2.7 160Example 37 25 60 110 2.5 130 Example 38 25 60 370 2.6 200 Example 39 2510 4300 2.5 45 Comparative 25 600 0 — — Example 1 Comparative 25 600 0 —— Example 2 Comparative 25 300 10 80 10 Example 3

TABLE 6 Solution (B Liquid) containing Solution (A Liquid) containingbromine-containing compound oxidizing agent and basic compound Bromine-Oxidizing Basic containing agent compound pH compound Example 24Tetramethylammonium Tetramethylammonium 12 Tetramethylammoniumhypochlorite hydroxide bromide (4.39 mass %, (0.09 mass %, (3.85 mass %,0.35 mol/L) 0.0097 mol/L) 0.25 mol/L) Example 25 TetramethylammoniumTetramethylammonium 12 Tetramethylammonium hypochlorite hydroxidebromide (11.66 mass %, (0.09 mass %, (1.1 mass %, 0.93 mol/L) 0.0097mol/L) 0.071 mol/L) Example 26 Tetramethylammonium Tetramethylammonium12 Tetramethylammonium hypochlorite hydroxide bromide (4.39 mass %,(0.09 mass %, (3.85 mass %, 0.35 mol/L) 0.0097 mol/L) 0.25 mol/L)Example 27 Tetramethylammonium Tetramethylammonium 12.8 hydrobromic acidhypochlorite hydroxide (2.0 mass %, (4.39 mass %, (0.70 mass %, 0.25mol/L) 0.35 mol/L) 0.075 mol/L) Example 28 TetramethylammoniumTetramethylammonium 12.5 Tetramethylammonium hypochlorite hydroxidebromide (4.39 mass %, (0.27 mass %, (3.85 mass %, 0.35 mol/L) 0.03mol/L) 0.25 mol/L) Example 29 Tetramethylammonium Tetramethylammonium 13Tetramethylammonium hypochlorite hydroxide bromide (4.39 mass %, (0.91mass %, (3.85 mass %, 0.35 mol/L) 0.0997 mol/L) 0.25 mol/L) Example 30Tetramethylammonium Tetramethylammonium 13 Tetramethylammoniumhypochlorite hydroxide bromide (0.788 mass %, (0.91 mass %, (19.25 mass%, 0.0625 mol/L) 0.0997 mol/L) 1.25 mol/L) Solution (B Liquid)containing bromine-containing compound Mixing pH Reaction Basic ratioMixing after time compound pH (A:B) method mixing [min] Example 24Tetramethylammonium 12 4:01 B was mixed 12 5 hydroxide into A (0.09 mass%, 0.0097 mol/L) Example 25 Tetramethylammonium 12 1.5:3.5  B was mixed12 5 hydroxide into A (0.09 mass %, 0.0097 mol/L) Example 26Tetramethylammonium 12 4:01 A was mixed 12 5 hydroxide into B (0.09 mass%, 0.0097 mol/L) Example 27 — 0.6 4:01 B was mixed 12 0 into A Example28 Tetramethylammonium 12.5 4:01 B was mixed 12.5 15 hydroxide into A(0.27 mass %, 0.03 mol/L) Example 29 Tetramethylammonium 13 4:01 B wasmixed 13 40 hydroxide into A (0.91 mass %, 0.0997 mol/L) Example 30Tetramethylammonium 13 4:01 B was mixed 13 15 hydroxide into A (0.91mass %, 0.0997 mol/L)

TABLE 7 Hypochlorite ion concentration Ion [%] pH pH 25% exchanged Cl2supply Reaction CO2 in gas immediately 10 before immediately ReactionTMAH water amount temperature phase after days reaction after efficiency[g] [g] [mL] [° C.] [ppm] production later step production [%] Example33 253 747 6810 11 <1 1.59 1.59 13.8 13.0 100 Example 34 253 747 6810 1150 1.59 1.59 13.8 12.5 100 Example 35 339 661 9478 25 <1 2.08 2.08 14.013.0 95

TABLE 8 Oxidation-reduction potential [V] pH ClO—/Cl— BrO—/Br— 8 1.241.11 10 1.13 1.00 12 1.01 0.88 14 0.89 0.76

TABLE 9 Tetraalkylammonium hydroxide Bromine ion sourceTetraalkylammonium bromide Example 36 Tetramethylammonium hydroxideHydrogen bromide Tetramethylammonium bromide (2.28 mass %, 0.25 mol/L)(2.02 mass %, 0.25 mol/L) (3.85 mass %, 0.25 mol/L)

1. A treatment liquid for a semiconductor with ruthenium, comprising ahypobromite ion, wherein the hypobromite ion content is 0.001 mol/L ormore and 0.20 mol/L or less. 2-3. (canceled)
 4. The treatment liquid fora semiconductor according to claim 1, wherein the treatment liquid for asemiconductor further comprises an oxidizing agent, and theoxidation-reduction potential of the oxidizing agent exceeds theoxidation-reduction potential of the hypobromite ion/Br⁻ system.
 5. Thetreatment liquid for a semiconductor according to claim 4, wherein theoxidizing agent contained in the treatment liquid for a semiconductor isa hypochlorite ion or ozone.
 6. The treatment liquid for a semiconductoraccording to claim 1, further comprising a tetraalkylammonium ion. 7.(canceled)
 8. The treatment liquid for a semiconductor according toclaim 1, wherein the proportion of the hypobromite ion in 1 mol ofbromine element contained in the treatment liquid for a semiconductor ismore than 0.5 mol.
 9. The treatment liquid for a semiconductor accordingto claim 1, wherein the treatment liquid has a pH of 8 or more and 14 orless.
 10. (canceled)
 11. A treatment liquid for a semiconductor withruthenium, comprising at least a bromine-containing compound, anoxidizing agent, a basic compound, and water, wherein the treatmentliquid has the bromine-containing compound added in an amount of 0.008mass % or more and less than 2.0 mass % as a bromine element contentwith respect to the total mass of the treatment liquid, has theoxidizing agent added in an amount of 0.1 mass ppm or more and 10 mass %or less with respect to the total mass, and has a pH of 8 or more and 14or less.
 12. The treatment liquid for a semiconductor with rutheniumaccording to claim 11, having the bromine-containing compound added inan amount of 0.08 mass % or more and less than 2.0 mass % as a bromineelement content.
 13. The treatment liquid for a semiconductor withruthenium according to claim 11, having the bromine-containing compoundadded in an amount of 0.01 mass % or more and less than 2 mass % as abromine element content, and having the oxidizing agent added in anamount of 0.1 mass % or more and 10 mass % or less.
 14. (canceled) 15.The treatment liquid for a semiconductor according to claim 11, whereinthe oxidizing agent is a hypochlorous acid compound or ozone.
 16. Thetreatment liquid for a semiconductor according to claim 11, wherein thebromine-containing compound is a bromine salt or hydrogen bromide. 17.The treatment liquid for a semiconductor according to claim 16, whereinthe bromine salt is a tetraalkylammonium bromide.
 18. (canceled)
 19. Thetreatment liquid for a semiconductor according to claim 11, wherein thebasic compound is a tetramethylammonium hydroxide.
 20. The treatmentliquid for a semiconductor according to claim 11, wherein the pH is 12or more and 14 or less. 21-25. (canceled)
 26. A method of producing thetreatment liquid for a semiconductor according to claim 11, comprising astep of mixing the bromine-containing compound and a solution containingboth the oxidizing agent and the basic compound.
 27. (canceled)
 28. Amethod of treating a substrate, comprising the steps of: producing atreatment liquid for a semiconductor by the production method accordingto claim 26; and then using the treatment liquid for a semiconductor toetch a ruthenium metal film and/or a ruthenium alloy film deposited onthe substrate.
 29. A method of producing a treatment liquid for asemiconductor with ruthenium, comprising a step of mixing a hypobromousacid, a hypobromite, a bromine water, or a bromine gas with a solutioncontaining a basic compound. 30-33. (canceled)
 34. The method ofproducing a treatment liquid for a semiconductor according to claim 29,wherein the basic compound is a tetramethylammonium hydroxide. 35-46.(canceled)
 47. The treatment liquid for a semiconductor according toclaim 4, wherein the proportion of the hypobromite ion in 1 mol ofbromine element contained in the treatment liquid for a semiconductor ismore than 0.5 mol.
 48. A treatment liquid for a semiconductor withruthenium, comprising at least a bromine-containing compound, anoxidizing agent, a basic compound, and water, wherein the treatmentliquid has the bromine-containing compound added in an amount of 0.008mass % or more and less than 2.0 mass % as a bromine element contentwith respect to the total mass of the treatment liquid, has theoxidizing agent added in an amount of 0.1 mass ppm or more and 10 mass %or less with respect to the total mass, and has a pH of 8 or more and 14or less, wherein the bromine-containing compound contains a hypobromiteion and one or more of HBrO₂, BrO₂ ⁻, HBrO₃, BrO₃ ⁻, and Br⁻, andwherein the concentration of the hypobromite ion is 0.001 mol/L or moreand 0.20 mol/L or less as the amount of the bromine element.
 49. Thetreatment liquid for a semiconductor according to claim 48, wherein theoxidizing agent is a hypochlorous acid compound or ozone.
 50. Thetreatment liquid for a semiconductor according to claim 48, wherein thebromine-containing compound contains a bromine salt or hydrogen bromide.51. The treatment liquid for a semiconductor according to claim 48,wherein the pH is 12 or more and 14 or less.
 52. The treatment liquidfor a semiconductor according to claim 48, wherein the proportion of thehypobromite ion in 1 mol of bromine element contained in the treatmentliquid for a semiconductor is more than 0.5 mol.
 53. A method ofproducing the treatment liquid for a semiconductor according to claim48, comprising a step of mixing the bromine-containing compound and asolution containing both the oxidizing agent and the basic compound. 54.A treatment liquid for a semiconductor with ruthenium, comprising atleast a bromine-containing compound, an oxidizing agent, a basiccompound, and water, wherein the treatment liquid has thebromine-containing compound added in an amount of 0.008 mass % or moreand less than 10 mass % as a bromine element content with respect to thetotal mass of the treatment liquid, has the oxidizing agent added in anamount of 0.1 mass ppm or more and 10 mass % or less with respect to thetotal mass, and has a pH of 8 or more and 14 or less, wherein theproportion of the hypobromite ion in 1 mol of bromine element containedin the treatment liquid for a semiconductor is more than 0.5 mol.
 55. Amethod of producing the treatment liquid for a semiconductor accordingto claim 54, comprising a step of mixing the bromine-containing compoundand a solution containing both the oxidizing agent and the basiccompound.
 56. A method of producing the treatment liquid for asemiconductor according to claim 54, comprising a step of mixing thebromine-containing compound into an aqueous solution of both theoxidizing agent and the basic compound.